Two Drosophila myosin transducer mutants with distinct cardiomyopathies have divergent ADP and actin affinities.

Bloemink, Marieke J. and Melkani, Girish C. and Dambacher, Corey M. and Bernstein, Sanford I. and Geeves, Michael A. (2011) Two Drosophila myosin transducer mutants with distinct cardiomyopathies have divergent ADP and actin affinities. Journal of Biological Chemistry, 286 (32). pp. 28435-28443. 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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Two Drosophila myosin II point mutations (D45 and Mhc(5)) generate Drosophila cardiac phenotypes that are similar to dilated or restrictive human cardiomyopathies. Our homology models suggest that the mutations (A261T in D45, G200D in Mhc(5)) could stabilize (D45) or destabilize (Mhc(5)) loop 1 of myosin, a region known to influence ADP release. To gain insight into the molecular mechanism that causes the cardiomyopathic phenotypes to develop, we determined whether the kinetic properties of the mutant molecules have been altered. We used myosin subfragment 1 (S1) carrying either of the two mutations (S1(A261T) and S1(G200D)) from the indirect flight muscles of Drosophila. The kinetic data show that the two point mutations have an opposite effect on the enzymatic activity of S1. S1(A261T) is less active (reduced ATPase, higher ADP affinity for S1 and actomyosin subfragment 1 (actin · S1), and reduced ATP-induced dissociation of actin · S1), whereas S1(G200D) shows increased enzymatic activity (enhanced ATPase, reduced ADP affinity for both S1 and actin · S1). The opposite changes in the myosin properties are consistent with the induced cardiac phenotypes for S1(A261T) (dilated) and S1(G200D) (restrictive). Our results provide novel insights into the molecular mechanisms that cause different cardiomyopathy phenotypes for these mutants. In addition, we report that S1(A261T) weakens the affinity of S1 · ADP for actin, whereas S1(G200D) increases it. This may account for the suppression (A261T) or enhancement (G200D) of the skeletal muscle hypercontraction phenotype induced by the troponin I held-up(2) mutation in Drosophila.

Item Type: Article
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: Sue Davies
Date Deposited: 03 Nov 2011 12:14
Last Modified: 29 Apr 2014 08:14
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