The slow skeletal muscle isoform of myosin shows kinetic features common to smooth and non-muscle myosins

Iorga, B. and Adamek, N. and Geeves, M.A. (2007) The slow skeletal muscle isoform of myosin shows kinetic features common to smooth and non-muscle myosins. Journal of Biological Chemistry, 282 (6). pp. 3559-3570. ISSN 0021-9258 . (The full text of this publication is not available from this repository)

The full text of this publication is not available from this repository. (Contact us about this Publication)
Official URL
http://www.jbc.org/cgi/reprint/282/6/3559

Abstract

Fast and slow mammalian muscle myosins differ in the heavy chain sequences (MHC-2, MHC-1) and muscles expressing the two isoforms contract at markedly different velocities. One role of slow skeletal muscles is to maintain posture with low ATP turnover, and MHC-1 expressed in these muscles is identical to heavy chain of the,beta-myosin of cardiac muscle. Few studies have addressed the biochemical kinetic properties of the slow MHC-1 isoform. We report here a detailed analysis of the MHC-1 isoform of the rabbit compared with MHC-2 and focus on the mechanism of ADP release. We show that MHC-1, like some non-muscle myosins, shows a biphasic dissociation of actin-myosin by ATP. Most of the actin-myosin dissociates at up to similar to 1000 s(-1), a very similar rate constant to MHC-2, but 10-15% of the complex must go through a slow isomerization (similar to 20 s(-1)) before ATP can dissociate it. Similar slow isomerizations were seen in the displacement of ADP from actinmyosin(.)ADP and provide evidence of three closely related actinmyosin(.)ADP complexes, a complex in rapid equilibrium with free ADP, a complex from which ADP is released at the rate required to define the maximum shortening velocity of slow muscle fibers (similar to 20 s(-1)), and a third complex that releases ADP too slowly (similar to 6 s(-1)) to be on the main ATPase pathway. The role of these actin-myosin(.)ADP complexes in the mechanochemistry of slow muscle contraction is discussed in relation to the load dependence of ADP release

Item Type: Article
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: Maureen Cook
Date Deposited: 31 Mar 2008 17:43
Last Modified: 14 Jan 2010 14:07
Resource URI: http://kar.kent.ac.uk/id/eprint/2535 (The current URI for this page, for reference purposes)
  • Depositors only (login required):