Proteins related to kinesin were first reported in early 1990, soon after the entry into the databases of the first kinesin protein to be cloned, kinesin heavy chain of Drosophila. The KRPs are related to kinesin by sequence similarity to the motor domain, a region of ~340 residues that consists of an ATP-binding site and an adjacent microtubule-binding site. The proteins typically show >35% sequence identity to the kinesin heavy chain motor domain but differ in amino acid sequence outside the motor domain. The sequence difference outside the motor domain is attributed to differences in function of the KRPs compared to kinesin.
Several of the KRPs have been demonstrated to be microtubule motor proteins that bind to and move on microtubules in in vitro motility assays. The motility characteristics of many of the proteins differ significantly from kinesin: the proteins differ from kinesin in velocity, and some of them have been found to move on microtubules with the opposite polarity as kinesin, toward microtubule minus instead of plus ends. Reversed polarity has been reported for members of the C-terminal motor subfamily (see Kinesin Tree page).
The cellular functions of the KRPs differ from those of kinesin, based on mutant analysis and localization. Several of the kinesin subfamilies, including KHC, Unc-104 and KRP85/95, have roles in vesicle/organelle transport. Evidence for transport of different types of vesicles/organelles by different classes of kinesin proteins is beginning to emerge. Strikingly, a large number of the KRPs are involved in spindle function and chromosome motility in mitosis and meiosis. These proteins could account for many of the movements of the spindle and chromosomes during cell division.
- Vallee, R.B. & Sheetz, M.P. (1996) Sci. 271, 1539-1544
- Bloom, G.S. & Endow, S.A. (1995) Prot. Profile 2, 1109-1171
- Pereira, A. & Goldstein, L.S.B. (1994) In Microtubules (ed. J.S. Hyams & C.W. Lloyd) pp 269-284, Wiley-Liss, NY
- M.A. Hoyt. (1994) Curr.Opin. Cell Biol. 6, 63-68
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Copyright 1996-2005. All rights reserved.
Created 7 July 1996 20:00 GMT
Modified 25 January 2005 21:20 GMT