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J. Biol. Chem., Vol. 280, Issue 13, 12299-12304, April 1, 2005

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The EB1 Homolog Mal3 Stimulates the ATPase of the Kinesin Tea2 by Recruiting It to the Microtubule^*

Heidi Browning and David D. Hackney

From the Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213

Tea2 is a kinesin family member from Schizosaccharomyces pombe that is targeted to microtubule tips and cell ends in a process that depends on Mal3. Constructs of Tea2 containing the motor domain only or the motor domain plus the N-terminal extension are monomeric, whereas a construct including the first predicted coiled coil region is dimeric. These constructs have a low basal rate of ATP hydrolysis of <0.1 s^–1, but microtubules stimulate the rate of ATP hydrolysis to a maximum of 15 s^–1. Hydrodynamic analysis of Mal3 indicates that it is dimeric. Mal3 is known to associate with Tea2, and analysis with the above Tea2 constructs indicates that the principal site of interaction of Mal3 with Tea2 is the N-terminal extension, although a weaker interaction is also observed with the motor domain alone. In parallel to the binding studies, Mal3 strongly stimulates the ATPase of constructs containing the N-terminal extension by decreasing the K_0.5(MT) for stimulation by microtubules but only weakly stimulates motor domains without the N-terminal extension. Mal3 reduces the K_0.5(MT) values without affecting the k_cat value at saturating microtubule level. Binding of Mal3 to microtubules induces an increase in the binding of Tea2 and a reciprocal stimulation of Mal3 binding by Tea2 is also observed. Tea2 is a plus end directed motor that drives sliding of axonemes when adsorbed to a glass surface. The sliding rate is initially unaffected by Mal3, but axonemes stop moving on continued exposure to Mal3.

Received for publication, December 3, 2004 , and in revised form, January 18, 2005.

^* This work was supported by National Institutes of Health Grant NS28562. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains a movie.

This work is dedicated to the memory of Heidi Browning who will be greatly missed.

To whom correspondence should be addressed: Dept. of Biological Sciences, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, PA 15213. Tel.: 412-268-3244; Fax: 412-268-7129; E-mail: ddh{at}andrew.cmu.edu.

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