A putative flagellar Ca2(+)-binding protein of the flagellum of trypanosomatid protozoan parasites.

Several cDNA clones of the protozoa Trypanosoma brucei and Trypanosoma lewisi were isolated as a reult of selection for evolutionarily conserved genes encoding cell-surface proteins (Lee and Van der Ploeg, unpublished). cDNA clone Tb-17 had a predicted open reading frame, encoding a 23 kDa protein (Figure 1A). This protein shared significant homology with a flagellar Ca binding protein (FCaBP) previously identified in Trypanosoma cruzi (1, Figure IB). The predicted Tb-17 protein encoded the 'E-F hand' Ca binding site homologous to the Ca binding site of Calmodulin in T. brucei (2, 3). Tb-17 is expressed at a relatively high level in both the bloodstream form and the insect form of T. brucei (data not shown). The evolutionary conservation, the presumed flagellar location and its potential Ca binding ability, suggest that this protein may play a role in cell motility or in Ca transport.