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Science 6 April 2007:
Vol. 316. no. 5821, pp. 120 - 123
DOI: 10.1126/science.1136985
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Reports

An ATP Gate Controls Tubulin Binding by the Tethered Head of Kinesin-1

Maria C. Alonso,1 Douglas R. Drummond,1 Susan Kain,1 Julia Hoeng,2 Linda Amos,2 Robert A. Cross1*

Kinesin-1 is a two-headed molecular motor that walks along microtubules, with each step gated by adenosine triphosphate (ATP) binding. Existing models for the gating mechanism propose a role for the microtubule lattice. We show that unpolymerized tubulin binds to kinesin-1, causing tubulin-activated release of adenosine diphosphate (ADP). With no added nucleotide, each kinesin-1 dimer binds one tubulin heterodimer. In adenylyl-imidodiphosphate (AMP-PNP), a nonhydrolyzable ATP analog, each kinesin-1 dimer binds two tubulin heterodimers. The data reveal an ATP gate that operates independently of the microtubule lattice, by ATP-dependent release of a steric or allosteric block on the tubulin binding site of the tethered kinesin-ADP head.

1 Molecular Motors Group, Marie Curie Research Institute, The Chart, Oxted, Surrey RH8 0TL, UK.
2 Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.

* To whom correspondence should be addressed. E-mail: r.cross{at}mcri.ac.uk

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