Glycophorin C
Encyclopedia
Glycophorin C plays a functionally important role in maintaining erythrocyte shape and regulating membrane material properties, possibly through its interaction with protein 4.1. Moreover, it has previously been shown that membranes deficient in protein 4.1 exhibit decreased content of glycophorin C. It is also an integral membrane protein
of the erythrocyte and acts as the receptor for the Plasmodium falciparum
protein PfEBP-2 (erythrocyte binding protein 2; baebl; EBA-140).
and glycophorin B
carry the blood group MN and Ss antigen
s respectively. There are ~225,000 molecules of GPC and GPD per erythrocyte.
Originally it was thought that glycophorin C and D were the result of a gene duplication event but it was only later realsed that that they were encoded by the same gene. Glycophorin D (GPD) is generated from the glycophorin C messenger RNA
by leaky translation at an in frame AUG at codon 30: glycophorin D = glycophorin
C residues 30 to 128. This leaky translation appears to be a uniquely human trait.
Glycophorin C (GPC) is a single polypeptide chain of 128 amino acids and is encoded by a gene
on the long arm of chromosome
2 (2q14-q21). The gene was first cloned in 1989 by High et al.. The GPC gene is organized in four exon
s distributed over 13.5 kilobase pairs of DNA
. Exon 1 encodes residues 1-16, exon 2 residues 17-35, exon 3 residues 36-63 and exon 4 residues 64-128. Exons 2 and 3 are highly homologous, with less than 5% nucleotide divergence. These exons also differ by a 9 amino acid insert at the 3' end of exon 3. The direct repeated segments containing these exons is 3.4 kilobase pairs long and may be derived from a recent duplication of a single ancestral domain. Exons 1, 2 and most of exon 3 encode the N-terminal extracellular domain while the remainder of exon 3 and exon 4 encode transmembrane and cytoplasmic domains.
Two isoforms are known and the gene is expressed in a wide variety of tissues
including kidney
, thymus
, stomach
, breast
, adult liver
and erythrocyte. In the non erythroid cell lines, expression is lower than in the erythrocyte and the protein is differentially glycosylated
. In the erythrocyte glycophorin C makes up ~4% of the membrane sialoglycoprotein
s. The average number of O linked chains is 12 per molecule.
The gene
is expressed early in the development of the erythrocyte, specifically in the erythroid burst-forming unit and erythroid colony-forming unit
. The mRNA from human erythroblasts is ~1.4 kilobases long and the transcription start site in erythroid cells has been mapped to 1050 base pairs 5' of the start codon. It is expressed early in developlment and before the Kell antigens, Rhesus-associated glycoprotein
, glycophorin A, band 3
, the Rhesus antigen and glycophorin B.
In melanocytic cells Glycophorin C gene expression may be regulated by MITF
.
GPC appears to be synthesized in excess in the erythrocyte and that the membrane content is regulated by band 4.1 (protein 4.1). Additional data on the regulation of glycophorin C is here.
In a study of this gene among the Hominoidea two finding unique to humans emerged: (1) an excess of non-synonymous divergence among species that appears to be caused solely by accelerated evolution and (2) the ability of the single GYPC gene to encode both the GPC and GPD proteins. The cause for this is not known but it was suggested that these findings might be the result of infection by Plasmodium falciparum.
and staining with periodic acid-Schiff staining (PAS) four glycophorins have been identified. These have been named glycophorin A, B, C and D in order of the quantity present in the membrane - gylycophorin A being the most and glycophorin D the least common. A fifth (glycophorin E
) has been identified within the human genome but cannot easily be detected on routine gel staining. In total the glycophorins constitute ~2% of the total erythrocyte membrane protein mass. Confusingly these proteins are also known under different nomenclatures but they are probably best known as the glycophorins.
Glycophorin C was first isolated in 1978 Glycophorin C and D are minor sialoglycoproteins contributing to 4% and 1% to the PAS-positive material and are present at about 2.0 and 0.5 x 105 copies/cell respectively. In polyacrylimide gels glycophorin C's apparent weight is 32 kilodaltons (32 kDa). Its structure is similar to that of other glycophorins: a highly glycoslated extracellular domain (residues 1-58), a transmembrane domain (residues 59-81) and an intracellular domain (residues 82-128). About 90% of the glycophorin C present in the erythrocyte is bound to the cytoskeleton and the remaining 10% moves freely within the membrane.
Glycophorin D's apparent molecular weight is 23kDa. On average this protein has 6 O linked oligosaccarides per molecule.
Within the erythrocyte it interacts with band 4.1
(an 80-kDa protein) and p55 (a palmitoylated
peripheral membrane phosphoprotein and a member of the membrane-associated guanylate kinase family) to form a ternary complex
that is critical for the shape and stability of erythrocytes. The major attachment sites between the erythrocyte spectrin
-actin
cytoskeleton
and the lipid bilayer are glycophorin C and band 3
. The interaction with band 4.1 and p55 is mediated by the N terminal 30 kD domain of band 4.1 binding to a 16 amino acid segment (residues 82-98: residues 61-77 of glycophorin D) within the cytoplasmic domain of glycophorin C and to a positively charged 39 amino acid motif in p55. The majority of protein 4.1 is bound to glycophorin C. The magnitude of the strength of the interaction between glycophorin C and band 4.1 has been estimated to be 6.9 microNewtons per meter, a figure typical of protein–protein interactions.
Glycophorin C normally shows oscillatory movement in the erythrocyte membrane. This is reduced in Southeast Asian ovalocytosis a disease of erythrocytes due to a mutation in band 3.
Glycophorin C and D encode the Gerbich (Ge) antigen
s. There are four allelles, Ge-1 to Ge-4. Three types of Ge antigen negativity are known: Ge-1,-2,-3 (Leach phenotype), Ge-2,-3 and Ge-2,+3. A 3.4 kilobase pair deletion within the gene, which probably arose because of unequal crossing over between the two repeated domains, is responsible for the formation of the Ge-2,-3 genotype
. The breakpoints of the deletion are located within intron
s 2 and 3 and results in the deletion of exon
3. This mutant gene is transcribed as a messenger RNA
with a continuous open reading frame
extending over 300 nucleotide
s and is translated into the sialoglycoprotein
found on Ge-2,-3 red cells. A second 3.4 kilobase pair deletion within the glycophorin C gene eliminates only exon 2 by a similar mechanism and generates the mutant gene
encoding for the abnormal glycoprotein found on Ge-2,+3 erythrocytes.
The Ge2 epitope is antigenic only on glycophorin D and is a cryptic antigen
in glycophorin C. It is located within exon 2 and is sensitive to trypsin
and papain
but resistant to chymotrypsin
and pronase
. The Ge3 epitope is encoded by exon 3. It is sensitive to trypsin
but resistant to chymotrypsin
, papain
and pronase
. It is thought to lie in the between amino acids 42-50 in glycophorin C (residues 21-49 in glycophorin D). Ge4 is located within the first 21 amino acids of glycophorin C. It is sensitive to trypsin, papain, pronase and neuraminidase
.
The relatively rare Leach phenotype is due either to a deletion in exons 3 and 4 or to a frameshift mutation
causing a premature stop codon in the glycophorin C gene, and persons with this phenotype are less susceptible (~60% of the control rate) to invasion by Plasmodium falciparum
. Such individuals have a subtype of a condition called hereditary elliptocytosis
.
The abnormally shaped cells are known as elliptocytes or cameloid cells. The basis for this phenotype was first reported by Telen et al.. The phenotype is Ge:-2,-3,-4.
The Yussef (Yus) phenotype
is due to a 57 base pair deletion corresponding to exon 2. The antigen is known as GPC Yus.
Glycophorin C mutations are rare in most of the Western world, but are more common in some places where malaria is endemic. In Melanesia
a greater percentage of the population is Gerbich negative (46.5%) than in any other part of the world. The incidence of Gerbich-negative phenotype caused by an exon 3 deletion in the Wosera (East Sepik Province) and Liksul (Madang Province
) populations of Papua New Guinea
is 0.463 and 0.176 respectively.
The rare Webb (Wb) antigen (~1/1000 donors), originally described in 1963 in Australia
, is the result of an alteration in glycosylation
of glycophorin C: an A to G transition at nucleotide 23 results in an asparagine
residue instead of the normal serine
residue with the resultant loss of glycoslation. The antigen is known as GPC Wb.
The rare Duch (Dh) antigen was discovered in Aarhus
, Denmark
(1968) and is also found on glycophorin C. It is due to a C to T transition
at nucleotide
40 resulting in the replacement of leucine
by phenylalanine
. This antigen is sensitive to trypsin but resistant to chymotrypsin and Endo F.
The Lewis II (Ls(a); Ge-6) antigen has insert of 84 nucleotides into the ancestral GPC gene: the insert corresponds to the entire sequence of exon 3. Two subtypes of this antigen are known: beta Ls(a) which carries the Ge3 epitope and gamma Ls(a) which carries both the Ge2 and Ge3 epitopes. This antigen is also known as the Rs(a) antigen.
The Ahonen (Ana) antigen was first reported in 1972.
The antigen is found on glycophorin D. This antigen was discovered in a Finnish man on May 5, 1968, during post operative blood cross matching for an aortic aneurism repair. In Finland the incidence of this antigen was found to be 6/10,000 donors. In Sweden the incidence was 2/3266 donors. The molecular basis for the origin of this antigen lies within exon 2 where a G->T substitution in codon 67 (base position 199) converts an alanine
to a serine
residue. While this epitope exists within glycophorin C there it is a cryptanitgen. It is only antigenic in glycophorin D because of the truncated N terminus.
A duplicated exon 2 has erythrocytes also been reported in Japanese blood donors (~2/10,000). This mutation has not been associated with a new anin was first noted in tigen.
Antibodies to the Gerbich antigens have been associated with transfusion reactions and mild hemolytic disease of the newborn.
In other stidies naturally occurring anti-Ge antibodies have been found and appear to be of no clinical significance. Immunological tolerance towards Ge antigen has been suggested.
Glycophorin C is the receptor for the protein erythrocyte binding antigen 140 (EBA140) of Plasmodium falciparum
. This interaction mediates a principal invasion pathway into the erythrocytes. The partial resistance of erythocytes lacking this protein to invasion by P. falciparum was first noted in 1982. The lack of Gerbich antigens in the population of Papua New Guinea was noted in 1989.
Influenza A and B bind to glycophorin C.
Integral membrane protein
An integral membrane protein is a protein molecule that is permanently attached to the biological membrane. Proteins that cross the membrane are surrounded by "annular" lipids, which are defined as lipids that are in direct contact with a membrane protein...
of the erythrocyte and acts as the receptor for the Plasmodium falciparum
Plasmodium falciparum
Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. It is transmitted by the female Anopheles mosquito. Malaria caused by this species is the most dangerous form of malaria, with the highest rates of complications and mortality...
protein PfEBP-2 (erythrocyte binding protein 2; baebl; EBA-140).
History
The antigen was discovered in 1960 when three women who lacked the antigen made anti-Gea in response to pregnancy. The antigen is named after one of the patients - a Mrs Gerbich. The following year a new but related antigen was discovered in a Mrs Yus for whom an antigen in this system is also named. In 1972 a numerical system for the antigens in this blood group was introduced.Genomics
Despite the similar names glycophorin C and D are unrelated to the other three glycophorins which encoded on chromosome 4 at location 4q28-q31. These latter proteins are closely related. Glycophorin AGYPA
Glycophorin A , also known as GYPA, is a protein which in humans is encoded by the GYPA gene. GYPA has also recently been designated CD235a .- Function :...
and glycophorin B
GYPB
Glycophorin B also known as sialoglycoprotein delta and SS-active sialoglycoprotein is a protein which in humans is encoded by the GYPB gene...
carry the blood group MN and Ss antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
s respectively. There are ~225,000 molecules of GPC and GPD per erythrocyte.
Originally it was thought that glycophorin C and D were the result of a gene duplication event but it was only later realsed that that they were encoded by the same gene. Glycophorin D (GPD) is generated from the glycophorin C messenger RNA
Messenger RNA
Messenger RNA is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes. Here, the nucleic acid polymer is translated into a polymer of amino acids: a protein...
by leaky translation at an in frame AUG at codon 30: glycophorin D = glycophorin
Glycophorin
A Glycophorin is a sialoglycoprotein of the membrane of a red blood cell. It is a membrane-spanning protein and carries sugar molecules. It is heavily glycosylated . Glycophorins are rich in sialic acid, which gives the red cells a very hydrophilic-charged coat...
C residues 30 to 128. This leaky translation appears to be a uniquely human trait.
Glycophorin C (GPC) is a single polypeptide chain of 128 amino acids and is encoded by a gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
on the long arm of chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
2 (2q14-q21). The gene was first cloned in 1989 by High et al.. The GPC gene is organized in four exon
Exon
An exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule either after portions of a precursor RNA have been removed by cis-splicing or when two or more precursor RNA molecules have been ligated by trans-splicing. The mature RNA molecule can be a messenger RNA...
s distributed over 13.5 kilobase pairs of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
. Exon 1 encodes residues 1-16, exon 2 residues 17-35, exon 3 residues 36-63 and exon 4 residues 64-128. Exons 2 and 3 are highly homologous, with less than 5% nucleotide divergence. These exons also differ by a 9 amino acid insert at the 3' end of exon 3. The direct repeated segments containing these exons is 3.4 kilobase pairs long and may be derived from a recent duplication of a single ancestral domain. Exons 1, 2 and most of exon 3 encode the N-terminal extracellular domain while the remainder of exon 3 and exon 4 encode transmembrane and cytoplasmic domains.
Two isoforms are known and the gene is expressed in a wide variety of tissues
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
including kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, thymus
Thymus
The thymus is a specialized organ of the immune system. The thymus produces and "educates" T-lymphocytes , which are critical cells of the adaptive immune system....
, stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
, breast
Breast
The breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.Both men and women develop breasts from the same embryological tissues...
, adult liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and erythrocyte. In the non erythroid cell lines, expression is lower than in the erythrocyte and the protein is differentially glycosylated
Glycosylation
Glycosylation is the reaction in which a carbohydrate, i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule . In biology glycosylation refers to the enzymatic process that attaches glycans to proteins, lipids, or other organic molecules...
. In the erythrocyte glycophorin C makes up ~4% of the membrane sialoglycoprotein
Sialoglycoprotein
A sialoglycoprotein is a combination of sialic acid and glycoprotein, which is, itself, a combination of sugar and protein.Glycophorin C is one common sialoglycoprotein....
s. The average number of O linked chains is 12 per molecule.
The gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
is expressed early in the development of the erythrocyte, specifically in the erythroid burst-forming unit and erythroid colony-forming unit
Colony-forming unit
In microbiology, colony-forming unit is a measure of viable bacterial or fungal numbers. Unlike direct microscopic counts where all cells, dead and living, are counted, CFU measures viable cells...
. The mRNA from human erythroblasts is ~1.4 kilobases long and the transcription start site in erythroid cells has been mapped to 1050 base pairs 5' of the start codon. It is expressed early in developlment and before the Kell antigens, Rhesus-associated glycoprotein
RHAG
Rh-associated glycoprotein is an ammonia transporter protein that in humans is encoded by the RHAG gene. RHAG has also recently been designated CD241 . Mutations in the RHAG gene can cause stomatocytosis....
, glycophorin A, band 3
Band 3
Anion Exchanger 1 or Band 3 is a phylogenetically preserved transport protein responsible for mediating the exchange of chloride for bicarbonate across a plasma membrane. Functionally similar members of the AE clade are AE2 and AE3.It is ubiquitous throughout the vertebrates...
, the Rhesus antigen and glycophorin B.
In melanocytic cells Glycophorin C gene expression may be regulated by MITF
Microphthalmia-associated transcription factor
Microphthalmia-associated transcription factor is a basic helix-loop-helix leucine zipper transcription factor involved in melanocyte and osteoclast development.-Clinical significance:...
.
GPC appears to be synthesized in excess in the erythrocyte and that the membrane content is regulated by band 4.1 (protein 4.1). Additional data on the regulation of glycophorin C is here.
In a study of this gene among the Hominoidea two finding unique to humans emerged: (1) an excess of non-synonymous divergence among species that appears to be caused solely by accelerated evolution and (2) the ability of the single GYPC gene to encode both the GPC and GPD proteins. The cause for this is not known but it was suggested that these findings might be the result of infection by Plasmodium falciparum.
Molecular biology
After separation of red cell membranes by SDS-polyacrylamide gel electrophoresisSDS-PAGE
SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis, describes a collection of related techniques widely used in biochemistry, forensics, genetics and molecular biology to separate proteins according to their electrophoretic mobility...
and staining with periodic acid-Schiff staining (PAS) four glycophorins have been identified. These have been named glycophorin A, B, C and D in order of the quantity present in the membrane - gylycophorin A being the most and glycophorin D the least common. A fifth (glycophorin E
GYPE
Glycophorin-E is a protein that in humans is encoded by the GYPE gene.-Further reading:...
) has been identified within the human genome but cannot easily be detected on routine gel staining. In total the glycophorins constitute ~2% of the total erythrocyte membrane protein mass. Confusingly these proteins are also known under different nomenclatures but they are probably best known as the glycophorins.
Glycophorin C was first isolated in 1978 Glycophorin C and D are minor sialoglycoproteins contributing to 4% and 1% to the PAS-positive material and are present at about 2.0 and 0.5 x 105 copies/cell respectively. In polyacrylimide gels glycophorin C's apparent weight is 32 kilodaltons (32 kDa). Its structure is similar to that of other glycophorins: a highly glycoslated extracellular domain (residues 1-58), a transmembrane domain (residues 59-81) and an intracellular domain (residues 82-128). About 90% of the glycophorin C present in the erythrocyte is bound to the cytoskeleton and the remaining 10% moves freely within the membrane.
Glycophorin D's apparent molecular weight is 23kDa. On average this protein has 6 O linked oligosaccarides per molecule.
Within the erythrocyte it interacts with band 4.1
Band 4.1
Protein 4.1, also known as Beatty's Protein, is a protein associated with the cytoskeleton that in humans is encoded by the EPB41 gene.Protein 4.1 is a major structural element of the erythrocyte membrane skeleton. It plays a key role in regulating membrane physical properties of mechanical...
(an 80-kDa protein) and p55 (a palmitoylated
Palmitoylation
S-Palmitoylation is the covalent attachment of fatty acids, such as palmitic acid, to cysteine residues of membrane proteins. The precise function of palmitoylation depends on the particular protein being considered. Palmitoylation enhances the hydrophobicity of proteins and contributes to their...
peripheral membrane phosphoprotein and a member of the membrane-associated guanylate kinase family) to form a ternary complex
Ternary complex
A Ternary complex refers to a protein complex containing three different molecules which are bound together. In structural biology ternary complex can be used to describe a crystal containing a protein with two small molecules bound, for example cofactor and substrate; or a complex formed between...
that is critical for the shape and stability of erythrocytes. The major attachment sites between the erythrocyte spectrin
Spectrin
Spectrin is a cytoskeletal protein that lines the intracellular side of the plasma membrane of many cell types in pentagonal or hexagonal arrangements, forming a scaffolding and playing an important role in maintenance of plasma membrane integrity and cytoskeletal structure...
-actin
Actin
Actin is a globular, roughly 42-kDa moonlighting protein found in all eukaryotic cells where it may be present at concentrations of over 100 μM. It is also one of the most highly-conserved proteins, differing by no more than 20% in species as diverse as algae and humans...
cytoskeleton
Cytoskeleton
The cytoskeleton is a cellular "scaffolding" or "skeleton" contained within a cell's cytoplasm and is made out of protein. The cytoskeleton is present in all cells; it was once thought to be unique to eukaryotes, but recent research has identified the prokaryotic cytoskeleton...
and the lipid bilayer are glycophorin C and band 3
Band 3
Anion Exchanger 1 or Band 3 is a phylogenetically preserved transport protein responsible for mediating the exchange of chloride for bicarbonate across a plasma membrane. Functionally similar members of the AE clade are AE2 and AE3.It is ubiquitous throughout the vertebrates...
. The interaction with band 4.1 and p55 is mediated by the N terminal 30 kD domain of band 4.1 binding to a 16 amino acid segment (residues 82-98: residues 61-77 of glycophorin D) within the cytoplasmic domain of glycophorin C and to a positively charged 39 amino acid motif in p55. The majority of protein 4.1 is bound to glycophorin C. The magnitude of the strength of the interaction between glycophorin C and band 4.1 has been estimated to be 6.9 microNewtons per meter, a figure typical of protein–protein interactions.
Glycophorin C normally shows oscillatory movement in the erythrocyte membrane. This is reduced in Southeast Asian ovalocytosis a disease of erythrocytes due to a mutation in band 3.
Transfusion medicine
These glycophorins are associated with eleven antigens of interest to transfusion medicine: the Gerbich (Ge2, Ge3, Ge4), the Yussef (Yus), the Webb (Wb or Ge5), the Duch (Dh(a) or Ge8), the Leach, the Lewis II (Ls(a) or Ge6), the Ahonen (An(a) or Ge7) and GEPL (Ge10*), GEAT (Ge11*) and GETI (Ge12*). Six are of high prevalence (Ge2, Ge3, Ge4, Ge10*, Ge11*, Ge12*) and five of low prevalence (Wb, Ls(a), An(a), Dh(a) and Ge9).Glycophorin C and D encode the Gerbich (Ge) antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
s. There are four allelles, Ge-1 to Ge-4. Three types of Ge antigen negativity are known: Ge-1,-2,-3 (Leach phenotype), Ge-2,-3 and Ge-2,+3. A 3.4 kilobase pair deletion within the gene, which probably arose because of unequal crossing over between the two repeated domains, is responsible for the formation of the Ge-2,-3 genotype
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...
. The breakpoints of the deletion are located within intron
Intron
An intron is any nucleotide sequence within a gene that is removed by RNA splicing to generate the final mature RNA product of a gene. The term intron refers to both the DNA sequence within a gene, and the corresponding sequence in RNA transcripts. Sequences that are joined together in the final...
s 2 and 3 and results in the deletion of exon
Exon
An exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule either after portions of a precursor RNA have been removed by cis-splicing or when two or more precursor RNA molecules have been ligated by trans-splicing. The mature RNA molecule can be a messenger RNA...
3. This mutant gene is transcribed as a messenger RNA
Messenger RNA
Messenger RNA is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes. Here, the nucleic acid polymer is translated into a polymer of amino acids: a protein...
with a continuous open reading frame
Open reading frame
In molecular genetics, an open reading frame is a DNA sequence that does not contain a stop codon in a given reading frame.Normally, inserts which interrupt the reading frame of a subsequent region after the start codon cause frameshift mutation of the sequence and dislocate the sequences for stop...
extending over 300 nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
s and is translated into the sialoglycoprotein
Sialoglycoprotein
A sialoglycoprotein is a combination of sialic acid and glycoprotein, which is, itself, a combination of sugar and protein.Glycophorin C is one common sialoglycoprotein....
found on Ge-2,-3 red cells. A second 3.4 kilobase pair deletion within the glycophorin C gene eliminates only exon 2 by a similar mechanism and generates the mutant gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
encoding for the abnormal glycoprotein found on Ge-2,+3 erythrocytes.
The Ge2 epitope is antigenic only on glycophorin D and is a cryptic antigen
Cryptotope
A cryptotope is an antigenic site or epitope hidden in protein or virion because it is present on the surface subunits that become buried. Cryptotopes are antigenically active only after disscociation of protein aggregates and virions...
in glycophorin C. It is located within exon 2 and is sensitive to trypsin
Trypsin
Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...
and papain
Papain
Papain, also known as papaya proteinase I, is a cysteine protease enzyme present in papaya and mountain papaya .-Papain family:...
but resistant to chymotrypsin
Chymotrypsin
Chymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin preferentially cleaves peptide amide bonds where the carboxyl side of the amide bond is a tyrosine, tryptophan, or phenylalanine. These amino acids contain an aromatic ring in their sidechain that fits into a...
and pronase
Pronase
Pronase is a commercially available mixture of proteinases isolated from the extracellular fluid of Streptomyces griseus. Activity extends to both denatured and native proteins leading to complete or nearly complete digestion into individual amino acids....
. The Ge3 epitope is encoded by exon 3. It is sensitive to trypsin
Trypsin
Trypsin is a serine protease found in the digestive system of many vertebrates, where it hydrolyses proteins. Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when...
but resistant to chymotrypsin
Chymotrypsin
Chymotrypsin is a digestive enzyme that can perform proteolysis. Chymotrypsin preferentially cleaves peptide amide bonds where the carboxyl side of the amide bond is a tyrosine, tryptophan, or phenylalanine. These amino acids contain an aromatic ring in their sidechain that fits into a...
, papain
Papain
Papain, also known as papaya proteinase I, is a cysteine protease enzyme present in papaya and mountain papaya .-Papain family:...
and pronase
Pronase
Pronase is a commercially available mixture of proteinases isolated from the extracellular fluid of Streptomyces griseus. Activity extends to both denatured and native proteins leading to complete or nearly complete digestion into individual amino acids....
. It is thought to lie in the between amino acids 42-50 in glycophorin C (residues 21-49 in glycophorin D). Ge4 is located within the first 21 amino acids of glycophorin C. It is sensitive to trypsin, papain, pronase and neuraminidase
Neuraminidase
Neuraminidase enzymes are glycoside hydrolase enzymes that cleave the glycosidic linkages of neuraminic acids. Neuraminidase enzymes are a large family, found in a range of organisms. The most commonly known neuraminidase is the viral neuraminidase, a drug target for the prevention of the spread...
.
The relatively rare Leach phenotype is due either to a deletion in exons 3 and 4 or to a frameshift mutation
Frameshift mutation
A frameshift mutation is a genetic mutation caused by indels of a number of nucleotides that is not evenly divisible by three from a DNA sequence...
causing a premature stop codon in the glycophorin C gene, and persons with this phenotype are less susceptible (~60% of the control rate) to invasion by Plasmodium falciparum
Plasmodium falciparum
Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. It is transmitted by the female Anopheles mosquito. Malaria caused by this species is the most dangerous form of malaria, with the highest rates of complications and mortality...
. Such individuals have a subtype of a condition called hereditary elliptocytosis
Hereditary elliptocytosis
Hereditary elliptocytosis, also known as ovalocytosis, is an inherited blood disorder in which an abnormally large number of the sufferer's erythrocytes are elliptical rather than the typical biconcave disc shape. It is one of many red-cell membrane defects. In its severe forms, this disorder...
.
The abnormally shaped cells are known as elliptocytes or cameloid cells. The basis for this phenotype was first reported by Telen et al.. The phenotype is Ge:-2,-3,-4.
The Yussef (Yus) phenotype
Phenotype
A phenotype is an organism's observable characteristics or traits: such as its morphology, development, biochemical or physiological properties, behavior, and products of behavior...
is due to a 57 base pair deletion corresponding to exon 2. The antigen is known as GPC Yus.
Glycophorin C mutations are rare in most of the Western world, but are more common in some places where malaria is endemic. In Melanesia
Melanesia
Melanesia is a subregion of Oceania extending from the western end of the Pacific Ocean to the Arafura Sea, and eastward to Fiji. The region comprises most of the islands immediately north and northeast of Australia...
a greater percentage of the population is Gerbich negative (46.5%) than in any other part of the world. The incidence of Gerbich-negative phenotype caused by an exon 3 deletion in the Wosera (East Sepik Province) and Liksul (Madang Province
Madang Province
Madang is a province on the northern coast of mainland Papua New Guinea. The province has many of the country's highest peaks, active volcanoes and its biggest mix of languages...
) populations of Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
is 0.463 and 0.176 respectively.
The rare Webb (Wb) antigen (~1/1000 donors), originally described in 1963 in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, is the result of an alteration in glycosylation
Glycosylation
Glycosylation is the reaction in which a carbohydrate, i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule . In biology glycosylation refers to the enzymatic process that attaches glycans to proteins, lipids, or other organic molecules...
of glycophorin C: an A to G transition at nucleotide 23 results in an asparagine
Asparagine
Asparagine is one of the 20 most common natural amino acids on Earth. It has carboxamide as the side-chain's functional group. It is not an essential amino acid...
residue instead of the normal serine
Serine
Serine is an amino acid with the formula HO2CCHCH2OH. It is one of the proteinogenic amino acids. By virtue of the hydroxyl group, serine is classified as a polar amino acid.-Occurrence and biosynthesis:...
residue with the resultant loss of glycoslation. The antigen is known as GPC Wb.
The rare Duch (Dh) antigen was discovered in Aarhus
Aarhus
Aarhus or Århus is the second-largest city in Denmark. The principal port of Denmark, Aarhus is on the east side of the peninsula of Jutland in the geographical center of Denmark...
, Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
(1968) and is also found on glycophorin C. It is due to a C to T transition
Transition (genetics)
In genetics, a transition is a point mutation that changes a purine nucleotide to another purine or a pyrimidine nucleotide to another pyrimidine . Approximately two out of three single nucleotide polymorphisms are transitions....
at nucleotide
Nucleotide
Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...
40 resulting in the replacement of leucine
Leucine
Leucine is a branched-chain α-amino acid with the chemical formula HO2CCHCH2CH2. Leucine is classified as a hydrophobic amino acid due to its aliphatic isobutyl side chain. It is encoded by six codons and is a major component of the subunits in ferritin, astacin and other 'buffer' proteins...
by phenylalanine
Phenylalanine
Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...
. This antigen is sensitive to trypsin but resistant to chymotrypsin and Endo F.
The Lewis II (Ls(a); Ge-6) antigen has insert of 84 nucleotides into the ancestral GPC gene: the insert corresponds to the entire sequence of exon 3. Two subtypes of this antigen are known: beta Ls(a) which carries the Ge3 epitope and gamma Ls(a) which carries both the Ge2 and Ge3 epitopes. This antigen is also known as the Rs(a) antigen.
The Ahonen (Ana) antigen was first reported in 1972.
The antigen is found on glycophorin D. This antigen was discovered in a Finnish man on May 5, 1968, during post operative blood cross matching for an aortic aneurism repair. In Finland the incidence of this antigen was found to be 6/10,000 donors. In Sweden the incidence was 2/3266 donors. The molecular basis for the origin of this antigen lies within exon 2 where a G->T substitution in codon 67 (base position 199) converts an alanine
Alanine
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
to a serine
Serine
Serine is an amino acid with the formula HO2CCHCH2OH. It is one of the proteinogenic amino acids. By virtue of the hydroxyl group, serine is classified as a polar amino acid.-Occurrence and biosynthesis:...
residue. While this epitope exists within glycophorin C there it is a cryptanitgen. It is only antigenic in glycophorin D because of the truncated N terminus.
A duplicated exon 2 has erythrocytes also been reported in Japanese blood donors (~2/10,000). This mutation has not been associated with a new anin was first noted in tigen.
Antibodies to the Gerbich antigens have been associated with transfusion reactions and mild hemolytic disease of the newborn.
In other stidies naturally occurring anti-Ge antibodies have been found and appear to be of no clinical significance. Immunological tolerance towards Ge antigen has been suggested.
Other areas
High expression of glycophorin C has been associated with a poor prognosis for acute lymphoblastic leukaemia in the Chinese.Glycophorin C is the receptor for the protein erythrocyte binding antigen 140 (EBA140) of Plasmodium falciparum
Plasmodium falciparum
Plasmodium falciparum is a protozoan parasite, one of the species of Plasmodium that cause malaria in humans. It is transmitted by the female Anopheles mosquito. Malaria caused by this species is the most dangerous form of malaria, with the highest rates of complications and mortality...
. This interaction mediates a principal invasion pathway into the erythrocytes. The partial resistance of erythocytes lacking this protein to invasion by P. falciparum was first noted in 1982. The lack of Gerbich antigens in the population of Papua New Guinea was noted in 1989.
Influenza A and B bind to glycophorin C.