title: Characterization of a membrane-associated rhoptry protein of Plasmodium falciparum.
abstract: Invasive forms of apicomplexan parasites contain secretory organelles called rhoptries that are essential for entry into host cells. We present a detailed characterization of an unusual rhoptry protein of the human malaria parasite Plasmodium falciparum, the rhoptry-associated membrane antigen (RAMA) that appears to have roles in both rhoptry biogenesis and host cell invasion. RAMA is synthesized as a 170-kDa protein in early trophozoites, several hours before rhoptry formation and is transiently localized within the endoplasmic reticulum and Golgi within lipid-rich microdomains. Regions of the Golgi membrane containing RAMA bud to form vesicles that later mature into rhoptries in a process that is inhibitable by brefeldin A. Other rhoptry proteins such as RhopH3 and RAP1 are found in close apposition with RAMA suggesting direct protein-protein interactions. We suggest that RAMA is involved in trafficking of these proteins into rhoptries. In rhoptries, RAMA is proteolytically processed to give a 60-kDa form that is anchored in the inner face of the rhoptry membrane by means of the glycosylphosphatidylinositol anchor. The p60 RAMA form is discharged from the rhoptries of free merozoites and binds to the red blood cell membrane by its most C-terminal region. In early ring stages RAMA is found in association with the parasitophorous vacuole.
authors: Department of Microbiology, Monash University, Wellington Road, Clayton 3800, Victoria, Australia.
authors: Agnieszka E
authors: AE
authors: Topolska
authors: Angela
authors: A
authors: Lidgett
authors: Dirk
authors: D
authors: Truman
authors: Hisashi
authors: H
authors: Fujioka
authors: Ross L
authors: RL
authors: Coppel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D016054:DNA, Protozoan / Q000235:genetics; D004912:Erythrocytes / Q000469:parasitology; D006801:Humans; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D016778:Malaria, Falciparum / Q000469:parasitology; D021962:Membrane Microdomains / Q000469:parasitology; D008969:Molecular Sequence Data; D015388:Organelles / Q000378:metabolism; D010963:Plasmodium falciparum / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000953:Antigens, Protozoan; D016054:DNA, Protozoan; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C065352:rhoptry associated protein, Plasmodium