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| Subject Categories: Membranes & Transport | Cell Cycle |
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| The EMBO Journal
(2003) 22, 1067–1074, doi:10.1093/emboj/cdg102 |
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| The human chromokinesin Kid is a plus end-directed microtubule-based motor |
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| Junichiro Yajima1, 2, Masaki Edamatsu1, Junko Watai-Nishii1, Noriko Tokai-Nishizumi3, Tadashi Yamamoto3 and Yoko Y. Toyoshima1 |
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1 Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan 2 Present address: Marie Curie Research Institute, The Chart, Oxted, Surrey RH8 0TL, UK 3 The Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-0071, Japan To whom correspondence should be addressed Yoko Y. Toyoshima, cyytoyo@mail.ecc.u-tokyo.ac.jp Received 22 October 2002; Revised 7 January 2003; Accepted 9 January 2003. |
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| Abstract |
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Kid is a kinesin-like DNA-binding protein known to be involved in chromosome movement during mitosis, although its actual motor function has not been demonstrated. Here, we describe the initial characterization of Kid as a microtubule-based motor using optical trapping microscopy. A bacterially expressed fusion protein consisting of a truncated Kid fragment (amino acids 1–388 or 1–439) is indeed an active microtubule motor with an average speed of  160 nm/s, and the polarity of movement is plus end directed. We could not detect processive movement of either monomeric Kid or dimerizing chimeric Kid; however, low levels of processivity (a few steps) cannot be detected with our method. These results are consistent with Kid having a role in chromosome congression in vivo, where it would be responsible for the polar ejection forces acting on the chromosome arms. |
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| Keywords: chromosome movement, kinesin-like protein, microtubule motor protein, mitosis, polar ejection force |
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