Maximum likelihood methods reveal conservation of function among closely related kinesin families

We have reconstructed the evolution of the anciently derived kinesin] super family using various alignment and tree-building methods. In addition to cl assifying previously described kinesins from protists. fungi. and animals. we analyzed a variety of kinesin sequences from the plant kingdom including 12 from Zea mays and 29 from Arabidopsis thaliana. Also included in Our da ta set were four sequences from the anciently diverged amitochondriate prot ist Giardia lamblia. The overall topology of the best tree we found is more likely than previously reported topologies and allows us to make the follo wing new observations: (1) kinesins involved in chromosome movement includi ng MCAK, chromokinesin, and CENP-E may be descended from a single ancestor. (2) kinesins that form complex oligomers are limited to a monophyletic gro up of families; (3) kinesins that crosslink antiparallel microtubules at th e spindle midzone including BIMC, MKLP, and CENP-E are closely related; (4) Drosophila NOD and human KID group with other characterized chromokinesins : and (5) Saccharomyces SMY1 groups with kinesin-I sequences, forming a fam ily of kinesins capable of class V myosin interactions. In addition, we fou nd that one monophyletic clade composed exclusively of sequences with a C-t erminal motor domain contains all known minus end-directed kinesins.