Shine-Dalgarno sequence
Encyclopedia
The Shine-Dalgarno sequence (or Shine-Dalgarno box), proposed by Australia
n scientists John Shine
(b.1946) and Lynn Dalgarno (b.1935), is a ribosomal
binding site in the mRNA, generally located 8 basepairs upstream
of the start codon
AUG. The Shine-Dalgarno sequence exists only in prokaryote
s. The six-base consensus sequence
is AGGAGG; in E. coli, for example, the sequence is AGGAGGU. This sequence helps recruit the ribosome to the mRNA to initiate protein synthesis by aligning it with the start codon
. The complementary sequence (CCUCCU), is called the anti-Shine-Dalgarno sequence and is located at the 3' end of the 16S
rRNA in the ribosome. The eukaryotic equivalent of the Shine-Dalgarno sequence is called the Kozak sequence
.
Mutation
s in the Shine-Dalgarno sequence can reduce translation. This reduction is due to a reduced mRNA-ribosome pairing efficiency, as evidenced by the fact that complementary mutations in the anti-Shine-Dalgarno sequence can restore translation.
When the Shine-Dalgarno sequence and anti-Shine-Dalgarno sequence pair, the translation initiation factor
s IF2-GTP, IF1, IF3, as well as the initiator tRNA fMet-tRNA(fmet
) are recruited to the ribosome.
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...
n scientists John Shine
John Shine
Professor John Shine AO is an Australian biochemist; he discovered the nucleotide sequence, called the Shine-Dalgarno sequence, necessary for the initiation of bacterial protein synthesis. He currently directs the Garvan Institute of Medical Research in Sydney, Australia.Shine was born in Brisbane...
(b.1946) and Lynn Dalgarno (b.1935), is a ribosomal
Ribosome
A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....
binding site in the mRNA, generally located 8 basepairs upstream
Upstream and downstream (DNA)
In molecular biology and genetics, upstream and downstream both refer to a relative position in DNA or RNA. Each strand of DNA or RNA has a 5' end and a 3' end, so named for the carbons on the deoxyribose ring. Relative to the position on the strand, downstream is the region towards the 3' end of...
of the start codon
Start codon
The start codon is generally defined as the point, sequence, at which a ribosome begins to translate a sequence of RNA into amino acids.When an RNA transcript is "read" from the 5' carbon to the 3' carbon by the ribosome the start codon is the first codon on which the tRNA bound to Met,...
AUG. The Shine-Dalgarno sequence exists only in prokaryote
Prokaryote
The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...
s. The six-base consensus sequence
Consensus sequence
In molecular biology and bioinformatics, consensus sequence refers to the most common nucleotide or amino acid at a particular position after multiple sequences are aligned. A consensus sequence is a way of representing the results of a multiple sequence alignment, where related sequences are...
is AGGAGG; in E. coli, for example, the sequence is AGGAGGU. This sequence helps recruit the ribosome to the mRNA to initiate protein synthesis by aligning it with the start codon
Start codon
The start codon is generally defined as the point, sequence, at which a ribosome begins to translate a sequence of RNA into amino acids.When an RNA transcript is "read" from the 5' carbon to the 3' carbon by the ribosome the start codon is the first codon on which the tRNA bound to Met,...
. The complementary sequence (CCUCCU), is called the anti-Shine-Dalgarno sequence and is located at the 3' end of the 16S
16S ribosomal RNA
16S ribosomal RNA is a component of the 30S subunit of prokaryotic ribosomes. It is approximately 1.5kb in length...
rRNA in the ribosome. The eukaryotic equivalent of the Shine-Dalgarno sequence is called the Kozak sequence
Kozak consensus sequence
The Kozak consensus sequence, Kozak consensus or Kozak sequence, is a sequence which occurs on eukaryotic mRNA and has the consensus gccRccAUGG, where R is a purine three bases upstream of the start codon , which is followed by another 'G'. The Kozak consensus sequence plays a major role in the...
.
Mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
s in the Shine-Dalgarno sequence can reduce translation. This reduction is due to a reduced mRNA-ribosome pairing efficiency, as evidenced by the fact that complementary mutations in the anti-Shine-Dalgarno sequence can restore translation.
When the Shine-Dalgarno sequence and anti-Shine-Dalgarno sequence pair, the translation initiation factor
Initiation factor
Initiation factors are proteins that bind to the small subunit of the ribosome during the initiation of translation, a part of protein biosynthesis.They are divided into three major groups:*Prokaryotic initiation factors*Archaeal initiation factors...
s IF2-GTP, IF1, IF3, as well as the initiator tRNA fMet-tRNA(fmet
N-Formylmethionine
N-Formylmethionine is a proteinogenic amino acid found in Bacteria and related Prokaryotic organelles. It is a derivative of the amino acid methionine in which a formyl group has been added to the amino group...
) are recruited to the ribosome.
The ribosomal S1 protein in Gram-negative bacteria
In Gram-negative bacteria, the presence of a Shine-Dalgarno sequence is not obligatory for the ribosome to locate the initiator codon. Numerous prokaryotic mRNAs don't possess Shine-Dalgarno sequences at all: ribosomal protein S1, which binds to AU-rich sequences found in many prokaryotic mRNAs 15-30 nucleotides upstream of start-codon, can instigate translation initiation in the case of these mRNAs.See also
- Kozak consensus sequenceKozak consensus sequenceThe Kozak consensus sequence, Kozak consensus or Kozak sequence, is a sequence which occurs on eukaryotic mRNA and has the consensus gccRccAUGG, where R is a purine three bases upstream of the start codon , which is followed by another 'G'. The Kozak consensus sequence plays a major role in the...
, the sequence that targets the ribosome to the initiation codon in eukaryoteEukaryoteA eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...
s. - Prokaryotic translationProkaryotic translationProkaryotic translation is the process by which messenger RNA is translated into proteins in prokaryotes.-Initiation:Initiation of translation in prokaryotes involves the assembly of the components of the translation system which are: the two ribosomal subunits , the mRNA to be translated, the...
External links
- http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=eurekah.section.19320