KAR3-encoded kinesin is a minus-end-directed motor that functions with centromere binding proteins (CBF3) on an in vitro yeast kinetochore.

We have used in vitro motility assays to investigate the mechanism of kinetochore function in the budding yeast Saccharomyces cerevisiae. Functional centromeric DNA plus a tripartite centromere binding protein complex, CBF3, was found to be necessary but not sufficient for in vitro kinetochore activity. A fourth required component was identified as the motor protein Kar3p, a previously reported yeast kinesin known to be involved in karyogamy and mitosis. Our data support genetic evidence suggesting that Kar3p is a kinetochore-associated motor and imply that CBF3 plays a regulatory role in kinetochore function.