A minus-end-directed kinesin with plus-end tracking protein activity is involved in spindle morphogenesis

Mol Biol Cell. 2005 Apr;16(4):1584-92. doi: 10.1091/mbc.e04-10-0935. Epub 2005 Jan 19.


Diverse kinesin motor proteins are involved in spindle function; however, the mechanisms by which they are targeted to specific sites within spindles are not well understood. Here, we show that a fusion between yellow fluorescent protein (YFP) and a minus-end-directed Kinesin-14 (C-terminal family) from Arabidopsis, ATK5, localizes to mitotic spindle midzones and regions rich in growing plus-ends within phragmoplasts. Notably, in Arabidopsis interphase cells, YFP::ATK5 localizes to microtubules with a preferential enrichment at growing plus-ends; indicating ATK5 is a plus-end tracking protein (+TIP). This +TIP activity is conferred by regions outside of the C-terminal motor domain, which reveals the presence of independent plus-end tracking and minus-end motor activities within ATK5. Furthermore, mitotic spindles of atk5 null mutant plants are abnormally broadened. Based on these data, we propose a model in which ATK5 uses plus-end tracking to reach spindle midzones, where it then organizes microtubules via minus-end-directed motor activity.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis / cytology*
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / metabolism*
  • Kinesins / chemistry
  • Kinesins / metabolism*
  • Microtubules / metabolism
  • Spindle Apparatus / chemistry
  • Spindle Apparatus / metabolism*


  • Arabidopsis Proteins
  • ATK5 protein, Arabidopsis
  • Kinesins