This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.105.075184v1 90/7/2427    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Swank, D. M. Articles by Maughan, D. W. Search for Related Content PubMed PubMed Citation Articles by Swank, D. M. Articles by Maughan, D. W.

An Alternative Domain Near the ATP Binding Pocket of Drosophila Myosin Affects Muscle Fiber Kinetics

Douglas M. Swank ^*, Joan Braddock , Waylon Brown , Heather Lesage , Sanford I. Bernstein  and David W. Maughan 

^* Department of Biology and Center for Biotechnology, Rensselaer Polytechnic Institute, Troy, New York; Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, Vermont; and Biology Department and Molecular Biology Institute, San Diego State University, San Diego, California

Correspondence: Address reprint requests to Dr. Douglas Swank, Dept. of Biology and Center for Biotechnology, Rensselaer Polytechnic Institute, Troy, NY 12180. Tel.: 518-276-4174; E-mail: swankd{at}rpi.edu.

We examined the importance of alternative versions of a region near the ATP binding site of Drosophila myosin heavy chain for muscle mechanical properties. Previously, we exchanged two versions of this region (encoded by alternative exon 7s) between the indirect flight muscle myosin isoform (IFI) and an embryonic myosin isoform (EMB) and found, surprisingly, that in vitro solution actin-activated ATPase rates were increased (higher V_max) by both exon exchanges. Here we examined the effect of increased ATPase rate on indirect flight muscle (IFM) fiber mechanics and Drosophila locomotion. IFM expressing EMB with the exon 7a domain replaced by the IFM specific exon 7d domain (EMB-7d) exhibited 3.2-fold greater maximum oscillatory power (P_max) and 1.5-fold greater optimal frequency of power generation (f_max) versus fibers expressing EMB. In contrast, IFM expressing IFI with the exon 7d region replaced by the EMB exon 7a region (IFI-7a), showed no change in P_max, f_max, step response, or isometric muscle properties compared to native IFI fibers. A slight decrement in IFI-7a flight ability was observed, suggesting a negative influence of the increased ATPase rate on Drosophila locomotion, perhaps due to energy supply constraints. Our results show that exon 7 plays a substantial role in establishing fiber speed and flight performance, and that the limiting step that sets ATPase rate in Drosophila myosin has little to no direct influence in setting f_max for fast muscle fiber types.

This article has been cited by other articles:

				B. M. Palmer, T. Suzuki, Y. Wang, W. D. Barnes, M. S. Miller, and D. W. Maughan Two-State Model of Acto-Myosin Attachment-Detachment Predicts C-Process of Sinusoidal Analysis Biophys. J., August 1, 2007; 93(3): 760 - 769. [Abstract] [Full Text] [PDF]