CpKLP1: A calmodulin-binding kinesin-like protein from Cyanophora paradoxa(Glaucophyta)

KCBP (kinesin-like calmodulin [CaM]-binding proteins), a member of the carb oxy-terminal kinesin-like proteins (KLPs), is unique among KLPs in having a CaM-binding domain (CBD), CaM-binding KLPs have been identified from flowe ring plants and the sea urchin, To determine if CaM-binding KLP is present in phylogenetically divergent protists, we probed Cyanophora paradoxa prote in extract with affinity-purified KCBP antibody, The KCBP antibody detected a polypeptide with a molecular mass of about 133 kDa in the crude extract, In a CaM-Sepharose column-purified fraction, the same band was detected wi th both KCBP antibody and biotinylated CaM, In a PCR reaction using degener ate primers corresponding to two conserved regions in the motor domain of k inesin, a 500-bp fragment (CpKLP1) was amplified from a cDNA library, The p redicted amino acid sequence of CpKLP1 showed significant sequence similari ty,vith KCBPs, In phylogenetic analysis, CpKLP1 fell into the KCBP group wi thin the carboxy-terminal subfamily, These biochemical data, sequence, and phylogenetic analysis strongly suggest the presence of a calmodulin-binding KLP in C. paradoxa and that it is related to Ca2+/calmodulin regulated KLP s from plants, This is the first report on identification of any motor prot ein in C. paradoxa. Furthermore, our data suggest that CaM-binding KLPs may have evolved long before the divergence of plants and animals.