Kinetic Mechanism of Myosin IXB and the Contributions of Two Class IX-specific Regions

Nalavadi, Vijayalaxmi and Nyitrai, Miklos and Bertolini, Cristina and Adamek, Nancy and Geeves, Michael A. and Bahler, Martin (2005) Kinetic Mechanism of Myosin IXB and the Contributions of Two Class IX-specific Regions. Journal of Biological Chemistry, 280 (47). pp. 38957-38968. ISSN 0021-9258. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Myosin IXb (Myo9b) was reported to be a single-headed, processive myosin. In its head domain it contains an N-terminal extension and a large loop 2 insertion that are specific for class IX myosins. We characterized the kinetic properties of purified, recombinant rat Myo9b, and we compared them with those of Myo9b mutants that had either the N-terminal extension or the loop 2 insertion deleted. Unlike other processive myosins, Myo9b exhibited a low affinity for ADP, and ADP release was not rate-limiting in the ATPase cycle. Myo9b is the first myosin for which ATP hydrolysis or an isomerization step after ATP binding is rate-limiting. Myo9b-ATP appeared to be in a conformation with a weak affinity for actin as determined by pyrene-actin fluorescence. However, in actin cosedimentation experiments, a subpopulation of Myo9b-ATP bound F-actin with a remarkably high affinity. Deletion of the N-terminal extension reduced actin affinity and increased the rate of nucleotide binding. Deletion of the loop 2 insertion reduced the actin affinity and altered the communication between actin and nucleotide-binding sites.

Item Type: Article
Additional information: 0021-9258 (Print) Journal Article
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: Michael Geeves
Date Deposited: 04 Apr 2009 19:32
Last Modified: 28 Apr 2014 15:34
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