MOLECULAR PHYLOGENY OF THE KINESIN FAMILY OF MICROTUBULE MOTOR PROTEINS

The rapidly expanding kinesin family of microtubule motor proteins inc ludes proteins that are involved in diverse microtubule-based function s in the cell. Phylogenetic analysis of the motor regions of the kines in proteins reveals at least five clearly defined groups that are like ly to identify kinesins with different roles in basic cellular process es. Two of the groups are consistent with overall sequence similarity, while two groups contain proteins that are related in overall structu re or function but show no significant sequence similarity outside the motor domain. One of these groups consists only of kinesin proteins w ith predicted C-terminal motor domains; another includes only kinesins required for mitotic spindle bipolarity. Drosophila Nod, presently an ungrouped protein, may represent a class of kinesins that, like the m yosin I proteins, function as monomers. The analysis indicates that ma ny types of kinesin proteins exist in eukaryotic organisms. At least t wo of the five groups identified in this analysis are expected to be p resent in most, or all, eukaryotes.