Kinetic Analysis of the Slow Skeletal Myosin MHC-1 Isoform from Bovine Masseter Muscle

Bloemink, Marieke J. and Adamek, Nancy and Reggiani, C. and Geeves, Michael A. (2007) Kinetic Analysis of the Slow Skeletal Myosin MHC-1 Isoform from Bovine Masseter Muscle. Journal of Molecular Biology, 373 (5). pp. 1184-1197. ISSN 00222836. (doi:https://doi.org/10.1016/j.jmb.2007.08.050 ) (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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Official URL
http://dx.doi.org/10.1016/j.jmb.2007.08.050

Abstract

Several heavy chain isoforms of class II myosins are found in muscle fibres and show a large variety of different mechanical activities. Fast myosins (myosin heavy chain (MHC)-II-2) contract at higher velocities than slow myosins (MHC-II-1, also known as beta-myosin) and it has been well established that ADP binding to actomyosin is much tighter for MHC-II-1 than for MHC-II-2. Recently, we reported several other differences between MHC-II isoforms 1 and 2 of the rabbit. Isoform II-1 unlike II-2 gave biphasic dissociation of actomyosin by ATP, the ATP-cleavage step was significantly slower for MHC-II-1 and the slow isoforms showed the presence of multiple actomyosin-ADP complexes. These results are in contrast to published data on MHC-II-1 from bovine left ventricle muscle, which was more similar to the fast skeletal isoform. Bovine MHC-II-1 is the predominant isoform expressed in both the ventricular myocardium and slow skeletal muscle fibres such as the masseter and is an important source of reference work for cardiac muscle physiology. This work examines and extends the kinetics of bovine MHC-II-1. We confirm the primary findings from the work on rabbit soleus MHC-II-1. Of significance is that we show that the affinity of ADP for bovine masseter myosin in the absence of actin (represented by the dissociation constant K(D)) is weaker than originally described for bovine cardiac myosin and thus the thermodynamic coupling between ADP and actin binding to myosin is much smaller (K(AD)/K(D) approximately 5 instead of K(AD)/K(D) approximately 50). This may indicate a distinct type of mechanochemical coupling for this group of myosin motors. We also find that the ATP-hydrolysis rate is much slower for bovine MHC-II-1 (19 s(-1)) than reported previously (138 s(-1)). We discuss how this work fits into a broader characterisation of myosin motors from across the myosin family.

Item Type: Article
Uncontrolled keywords: subfragment 1; actin; ATPase; strain-sensor; ADP
Subjects: Q Science
Divisions: Faculties > Sciences > School of Biosciences
Depositing User: Michael Geeves
Date Deposited: 16 Aug 2009 17:12 UTC
Last Modified: 28 Apr 2014 15:36 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/13216 (The current URI for this page, for reference purposes)
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