Kar3Vik1, a member of the kinesin-14 superfamily, shows a novel kinesin microtubule binding pattern.
Kinesin-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 αβ-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.
Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA.
Katherine C
KC
Rank
Chun Ju
CJ
Chen
Julia
J
Cope
Ken
K
Porche
Andreas
A
Hoenger
Susan P
SP
Gilbert
Ivan
I
Rayment
D000244:Adenosine Diphosphate / Q000378:metabolism; D020285:Cryoelectron Microscopy; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D016547:Kinesins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008870:Microtubules / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
D005656:Fungal Proteins; C063504:KAR3 protein, S cerevisiae; D008869:Microtubule-Associated Proteins; D029701:Saccharomyces cerevisiae Proteins; C119241:VIK1 protein, S cerevisiae; D000244:Adenosine Diphosphate; D016547:Kinesins