A NEW KINESIN-LIKE PROTEIN (KLP1) LOCALIZED TO A SINGLE MICROTUBULE OF THE CHLAMYDOMONAS-FLAGELLUM

The kinesin superfamily of mechanochemical proteins has been implicate d in a wide variety of cellular processes. We have begun studies of ki nesins in the unicellular biflagellate alga, Chlamydomonas reinhardtii . A full-length cDNA, KLP1, has been cloned and sequenced, and found t o encode a new member of the kinesin superfamily. An antibody was rais ed against the nonconserved tail region of the Klp1 protein, and it wa s used to probe for Klp1 in extracts of isolated flagella and in situ. Immunofluorescence of whole cells indicated that Klp1 was present in both the flagella and cell bodies. In wild-type flagella, Klp1 was bou nd tightly to the axoneme; immunogold labeling of wild-type axonemal w hole mounts showed that Klp1 was restricted to one of the two central pair microtubules at the core of the axoneme. Klp1 was absent from the flagella of mutants lacking the central pair microtubules, but was pr esent in mutant flagella from pf16 cells, which contain an unstable C1 microtubule, indicating that Klp1 was bound to the C2 central pair mi crotubule. Localization of Klp1 to the C2 microtubule was confirmed by immunogold labeling of negatively stained and thin-sectioned axonemes . These findings suggest that Klp1 may play a role in rotation or twis ting of the central pair microtubules.