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 .
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| 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) |
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