In molecular biology, apical membrane antigen 1 is a novel 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...

 of Plasmodium

Plasmodium

Plasmodium is a genus of parasitic protists. Infection by these organisms is known as malaria. The genus Plasmodium was described in 1885 by Ettore Marchiafava and Angelo Celli. Currently over 200 species of this genus are recognized and new species continue to be described.Of the over 200 known...

 falciparum which has been cloned

Molecular cloning

Molecular cloning refers to a set of experimental methods in molecular biology that are used to assemble recombinant DNA molecules and to direct their replication within host organisms...

. It contains a hydrophobic domain typical of an integral membrane protein

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...

. The antigen is designated apical

Apical

Apical, from the Latin apex meaning to be at the apex or tip, may refer to:*Apical , an anatomical term of location for features associated with the base of an organism or structure...

 membrane antigen 1 (AMA-1) by virtue of appearing to be located in the apical complex

Protein complex

A multiprotein complex is a group of two or more associated polypeptide chains. If the different polypeptide chains contain different protein domain, the resulting multiprotein complex can have multiple catalytic functions...

. AMA-1 appears to be transported to the merozoite surface close to the time of schizont rupture.

The 66kDa merozoite surface antigen (PK66) of Plasmodium knowlesi, a simian malaria, possesses vaccine-related properties believed to originate from a receptor-like role in parasite invasion of erythrocytes. The sequence

Sequence (biology)

A sequence in biology is the one-dimensional ordering of monomers, covalently linked within in a biopolymer; it is also referred to as the primary structure of the biological macromolecule.-See also:* Protein sequence* DNA sequence...

 of PK66 is conserved

Conserved sequence

In biology, conserved sequences are similar or identical sequences that occur within nucleic acid sequences , protein sequences, protein structures or polymeric carbohydrates across species or within different molecules produced by the same organism...

 throughout plasmodium, and shows high similarity to P. falciparum AMA-1. Following schizont rupture, the distribution of PK66 changes in a coordinate manner associated with merozoite invasion. Prior to rupture, the protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 is concentrated at the apical end, following which it distributes itself entirely across the surface of the free merozoite. Immunofluorescence

Immunofluorescence

Immunofluorescence is a technique used for light microscopy with a fluorescence microscope and is used primarily on biological samples. This technique uses the specificity of antibodies to their antigen to target fluorescent dyes to specific biomolecule targets within a cell, and therefore allows...

studies suggest that, during invasion, PK66 is excluded from the erythrocyte at, and behind, the invasion interface.