A novel EF-hand calcium-binding protein in the flagellum of the protozoan Tritrichomonas suis

The cloning and characterization of Ts-p41, an EF-hand calcium-binding prot ein of the protozoan parasite Tritrichomonas suis is described double dagge r. A T. suis cDNA library was screened with monospecific antibodies affinit y purified on an immunoreactive 41 kDa antigen in a Triton X-114 membrane-p rotein fraction. The resulting cDNA fragments turned out to be derived from 2 different genes encoding closely related Ts-p41 variants. The deduced am ino acid sequences contained 6 EF-hand domains perfectly matching the canon ical consensus motif and a putative C-terminal prenylation site. Northern a nd Southern hybridizations revealed that Ts-p41 was highly expressed and en coded by a gene-family. A cDNA encoding Ts-p41 was expressed as recombinant protein in Escherichia roll. By overlay with Ca-45 it was demonstrated tha t the native and recombinant Ts-p41 proteins bind Ca2+. In immunofluorescen ce, epitopes recognized by anti-Ts-p41 antibodies were distributed as well on the anterior flagella as on the recurrent flagellum of the parasite. Our findings with the parabasalid T. suis suggest that multiple EF-hand bearin g calcium-binding proteins might be a common phenomenon associated with fla gellar motility.