Loop 1 of transducer region in mammalian class I myosin, Myo1b, modulates actin affinity, ATPase activity, and nucleotide access

Clark, R. and Ansari, M.A. and Dash, S. and Geeves, M.A. and Coluccio, L.M. (2005) Loop 1 of transducer region in mammalian class I myosin, Myo1b, modulates actin affinity, ATPase activity, and nucleotide access. Journal of Biological Chemistry, 280 (35). pp. 30935-42. ISSN 0021-9258. (The full text of this publication is not available from this repository)

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Official URL
http://www.jbc.org/cgi/content/abstract/280/35/309...

Abstract

Loop 1, a flexible surface loop in the myosin motor domain, comprises in part the transducer region that lies near the nucleotide-binding site and is proposed from structural studies to be responsible for the kinetic tuning of product release following ATP hydrolysis (1). Biochemical studies have shown that loop 1 affects the affinity of actin-myosin-II for ADP, motility and the V(max) of the actin-activated Mg2+-ATPase activity, possibly through P(i) release (2-8). To test the influence of loop 1 on the mammalian class I myosin, Myo1b, chimeric molecules in which (i) loop 1 of a truncated form of Myo1b, Myo1b1IQ, was replaced with either loop 1 from other myosins; (ii) loop 1 was replaced with glycine; or (iii) some amino acids in the loop were substituted with alanine and were expressed in baculovirus, and their interactions with actin and nucleotide were evaluated. The steady-state actin-activated ATPase activity; rate of ATP-induced dissociation of actin from Myo1b1IQ; rate of ADP release from actin-Myo1b1IQ; and the affinity of actin for Myo1b1IQ and Myo1b1IQ.ADP differed in the chimeras versus wild type, indicating that loop 1 has a much wider range of effects on the coupling between actin and nucleotide binding events than previously thought. In particular, the biphasic ATP-induced dissociation of actin from actin-Myo1b1IQ was significantly altered in the chimeras. This provided evidence that loop 1 contributes to the accessibility of the nucleotide pocket and is involved in the integration of information from the actin-, nucleotide-, gamma-P(i)-, and calmodulin-binding sites and predicts that loop 1 modulates the load dependence of the motor.

Item Type: Article
Additional information: 0021-9258 (Print) Journal Article
Uncontrolled keywords: Actins/*metabolism Adenosine Diphosphate/metabolism Adenosine Triphosphate/metabolism Amino Acid Sequence Animals Ca(2+) Mg(2+)-ATPase/*metabolism Fluorescent Dyes/metabolism Models, Molecular Molecular Sequence Data Myosin Type I/*chemistry/genetics/*metabolism Nucleotides/*metabolism Phalloidine/metabolism Protein Binding *Protein Structure, Secondary Protein Structure, Tertiary Pyrenes/metabolism Rats Recombinant Fusion Proteins/chemistry/genetics/metabolism Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. Sequence Alignment
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: Michael Geeves
Date Deposited: 04 Apr 2009 18:59
Last Modified: 04 Apr 2009 18:59
Resource URI: http://kar.kent.ac.uk/id/eprint/13204 (The current URI for this page, for reference purposes)
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