title: A novel flagellar Ca2+-binding protein in trypanosomes.
abstract: A 24-kDa protein of Trypanosoma cruzi, the protozoan parasite that causes Chagas' disease, is recognized by antisera from both humans and experimental animals infected with this organism. Near its C terminus are two regions that have sequence similarity with several Ca2+-binding proteins and that conform to the "E-F hand" Ca2+-binding structure. We expressed a cDNA encoding this protein in Escherichia coli and showed that both the recombinant protein and the 24-kDa native trypanosome protein do indeed bind Ca2+. The protein's low Ca2+-binding capacity (less than 2 mol of Ca2+/mol of protein) and high Ca2+-binding affinity (apparent Kd less than 50 microM Ca2+) are consistent with binding of Ca2+ via the E-F hand structures. Immunofluorescence assays using a mouse antiserum directed against the fusion protein localized the native protein to the trypanosome's flagellum. The protein's abundance, Ca2+-binding property, and flagellar localization suggest that it participates in molecular processes associated with the high motility of the parasite.
authors.affiliation: Department of Biochemistry, University of Iowa, Iowa City.
authors.forename: D M
authors.initials: DM
authors.lastname: Engman
authors.forename: K H
authors.initials: KH
authors.lastname: Krause
authors.forename: J H
authors.initials: JH
authors.lastname: Blumin
authors.forename: K S
authors.initials: KS
authors.lastname: Kim
authors.forename: L V
authors.initials: LV
authors.lastname: Kirchhoff
authors.forename: J E
authors.initials: JE
authors.lastname: Donelson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D002155:Calsequestrin / Q000378:metabolism; D004247:DNA / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005407:Flagella / Q000032:analysis*; D005455:Fluorescent Antibody Technique; D008969:Molecular Sequence Data; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D014349:Trypanosoma cruzi / Q000032:analysis*
chemical_list: D002135:Calcium-Binding Proteins; D002155:Calsequestrin; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C061478:flagellar calcium-binding protein, Trypanosoma cruzi; D004247:DNA; D002118:Calcium