KINESIN PROTEINS - A PHYLUM OF MOTORS FOR MICROTUBULE-BASED MOTILITY

The cellular processes of transport, division and, possibly, early dev elopment all involve microtubule-based motors. Recent work shows that, unexpectedly, many of these cellular functions are carried out by dif ferent types of kinesin and kinesin-related motor proteins. The kinesi n proteins are a large and rapidly growing family of microtubule-motor proteins that share a 340-amino-acid motor domain. Phylogenetic analy sis of the conserved motor domains groups the kinesin proteins into a number of subfamilies, the members of which exhibit a common molecular organization and related functions. The kinesin proteins that belong to different subfamilies differ in their rates and polarity of movemen t along microtubules, and probably in the particles/organelles that th ey transport. The kinesins arose early in eukaryotic evolution and gen e duplication has allowed functional specialization to occur, resultin g in a surprisingly large number of different classes of these protein s adapted for intracellular transport of vesicles and organelles, and for assembly and force generation in the meiotic and mitotic spindles.