Kar3 interaction with Cik1 alters motor structure and function.

Published

Journal Article

Kar3, a kinesin-14 motor of Saccharomyces cerevisiae required for mitosis and karyogamy, reportedly interacts with Cik1, a nonmotor protein, via its central, predicted coiled coil. Despite this, neither Kar3 nor Cik1 homodimers have been observed in vivo. Here we show that Kar3 is a dimer in vitro by analytical ultracentrifugation. The motor domains appear as paired particles by rotary-shadow electron microscopy (EM) and circular dichroism (CD) spectroscopy of the nonmotor region shows characteristics of helical structure, typical of coiled coils. Remarkably, the Kar3/Cik1 nonmotor region shows greater helicity by CD analysis and rotary-shadow EM reveals a stalk joined to one large or two smaller particles. The highly helical Kar3/Cik1 nonmotor region and visible stalk indicate that dimerization with Cik1 causes structural changes in Kar3. The Cik1 and Kar3 stalk regions preferentially associate with one another rather than forming homodimers. Kar3/Cik1 moves on microtubules at 2-2.4 microm min(-1), 2-5-fold faster than Kar3, and destabilizes microtubules at the lagging ends. Thus, structural changes in Kar3 upon dimerization with Cik1 alter the motor velocity and likely regulate Kar3 activity in vivo.

Full Text

Duke Authors

Cited Authors

  • Chu, HMA; Yun, M; Anderson, DE; Sage, H; Park, H-W; Endow, SA

Published Date

  • September 21, 2005

Published In

Volume / Issue

  • 24 / 18

Start / End Page

  • 3214 - 3223

PubMed ID

  • 16107877

Pubmed Central ID

  • 16107877

International Standard Serial Number (ISSN)

  • 0261-4189

Digital Object Identifier (DOI)

  • 10.1038/sj.emboj.7600790

Language

  • eng

Conference Location

  • England