Characterization of a cDNA encoding a cysteine-rich cell surface protein located in the flagellar pocket of the protozoan Trypanosoma brucei.
We have characterized a cDNA encoding a cysteine-rich, acidic integral membrane protein (CRAM) of the parasitic protozoa Trypanosoma brucei and Trypanosoma equiperdum. Unlike other membrane proteins of T. brucei, which are distributed throughout the cell surface, CRAM is concentrated in the flagellar pocket, an invagination of the cell surface of the trypanosome where endocytosis has been documented. Accordingly, CRAM also locates to vesicles located underneath the pocket, providing evidence of its internalization. CRAM has a predicted molecular mass of 130 kilodaltons and has a signal peptide, a transmembrane domain, and a 41-amino-acid cytoplasmic extension. A characteristic feature of CRAM is a large extracellular domain with a roughly 66-fold acidic, cysteine-rich 12-amino-acid repeat. CRAM is conserved among different protozoan species, including Trypanosoma cruzi, and CRAM has structural similarities with eucaryotic cell surface receptors. The most striking homology of CRAM is to the human low-density-lipoprotein receptor. We propose that CRAM functions as a cell surface receptor of different trypanosome species.
Department of Genetics and Development, Columbia University, New York, New York 10032.
M G
MG
Lee
B E
BE
Bihain
D G
DG
Russell
R J
RJ
Deckelbaum
L H
LH
Van der Ploeg
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics* / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D015151:Immunoblotting; D008297:Male; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000032:analysis / Q000235:genetics*; D012313:RNA / Q000235:genetics* / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014346:Trypanosoma brucei brucei / Q000235:genetics* / Q000648:ultrastructure
D008565:Membrane Proteins; D015800:Protozoan Proteins; C065453:cysteine-rich, acidic integral membrane protein, Trypanosoma brucei; D012313:RNA; D004247:DNA