title: Novel putative glycosylphosphatidylinositol-anchored micronemal antigen of Plasmodium falciparum that binds to erythrocytes.
abstract: We have identified a new Plasmodium falciparum erythrocyte binding protein that appears to be located in the micronemes of the merozoite stage of the parasite and membrane linked through a glycosylphosphatidylinositol (GPI) anchor. The protein is designated GPI-anchored micronemal antigen (GAMA) and was identified by applying a set of selection criteria to identify previously uncharacterized merozoite proteins that may have a role in cell invasion. The protein is also present in the proteomes of the sporozoite and ookinete micronemes and is conserved throughout the genus. GAMA contains a novel domain that may be constrained by disulfide bonds and a predicted C-terminal hydrophobic sequence that is presumably replaced by the GPI. The protein is synthesized late during schizogony, processed into two fragments that are linked by a disulfide bond, and translocated to an apical location, which is probably the micronemes. In a proportion of free merozoites GAMA can also be detected on the parasite surface. Following erythrocyte invasion the bulk of the protein is shed in a soluble form, although a short C-terminal fragment may be carried into the newly invaded red blood cell. The protein was shown to bind reversibly to erythrocytes and therefore represents a new example of a host cell binding protein.
authors.affiliation: Division of Parasitology, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, UK.
authors.forename: Louise
authors.initials: L
authors.lastname: Hinds
authors.forename: Judith L
authors.initials: JL
authors.lastname: Green
authors.forename: Ellen
authors.initials: E
authors.lastname: Knuepfer
authors.forename: Munira
authors.initials: M
authors.lastname: Grainger
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Holder
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity; D002478:Cells, Cultured; D004912:Erythrocytes / Q000166:cytology / Q000378:metabolism* / Q000469:parasitology*; D005455:Fluorescent Antibody Technique; D017261:Glycosylphosphatidylinositols / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008018:Life Cycle Stages; D052940:Merozoites / Q000166:cytology / Q000378:metabolism; D010271:Parasites / Q000166:cytology / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D010963:Plasmodium falciparum / Q000166:cytology / Q000254:growth & development / Q000276:immunology* / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D052939:Schizonts / Q000166:cytology / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D000953:Antigens, Protozoan; D017261:Glycosylphosphatidylinositols; D010455:Peptides