4etp
From Proteopedia
C-terminal motor and motor homology domain of Kar3Vik1 fused to a synthetic heterodimeric coiled coil
Structural highlights
FunctionKAR3_YEAST Essential for yeast nuclear fusion during mating. KAR3 is a bifunctional protein having a kinesin-like motor domain joined to a distinct microtubule binding domain. It may mediate microtubule sliding during nuclear fusion and possibly mitosis. May interact with spindle microtubules to produce an inwardly directed force acting upon the poles. KAR3 function antagonizes CIP8 and KIP1 outward force action. KAR3 motor activity is directed toward the microtubule's minus end.[1] [2] Publication Abstract from PubMedKinesin-14 motors generate microtubule minus-end-directed force used in mitosis and meiosis. These motors are dimeric and operate with a nonprocessive powerstroke mechanism, but the role of the second head in motility has been unclear. In Saccharomyces cerevisiae, the Kinesin-14 Kar3 forms a heterodimer with either Vik1 or Cik1. Vik1 contains a motor homology domain that retains microtubule binding properties but lacks a nucleotide binding site. In this case, both heads are implicated in motility. Here, we show through structural determination of a C-terminal heterodimeric Kar3Vik1, electron microscopy, equilibrium binding, and motility that at the start of the cycle, Kar3Vik1 binds to or occludes two alphabeta-tubulin subunits on adjacent protofilaments. The cycle begins as Vik1 collides with the microtubule followed by Kar3 microtubule association and ADP release, thereby destabilizing the Vik1-microtubule interaction and positioning the motor for the start of the powerstroke. The results indicate that head-head communication is mediated through the adjoining coiled coil. Kar3Vik1, a member of the kinesin-14 superfamily, shows a novel kinesin microtubule binding pattern.,Rank KC, Chen CJ, Cope J, Porche K, Hoenger A, Gilbert SP, Rayment I J Cell Biol. 2012 Jun 25;197(7):957-70. doi: 10.1083/jcb.201201132. PMID:22734002[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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