Blog
About

1
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      Regulation of Smooth Muscle Actomyosin

      Read this article at

      ScienceOpenPublisher
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          In smooth muscle it is generally accepted that at the level of the contractile apparatus regulation is achieved by activating a dormant state in the presence of Ca<sup>2+</sup>. This event initiates the contractile process which is manifest by an increased cross-bridge cycling rate and the development of tension, or in biochemical terms, by an increase in the activation by actin of the Mg<sup>2+</sup>-ATPase activity of myosin. A controversy exists, however, on the identity of the activator, and this review considers the two proposed possibilities. One theory is based on the phosphorylation and dephosphorylation of the 20,000 dalton molecular weight myosin light chains. It is assumed that in the phosphorylated state the Mg<sup>2+</sup>-ATPase activity of myosin can be activated by actin whereas dephosphorylated myosin cannot be activated by actin. Phosphorylation of myosin, and hence the activation of the contractile apparatus, is achieved by a myosin light chain kinase, and it has been shown that the calcium dependence of the phosphorylation reaction resides with one of the two components of this enzyme, namely calmodulin. Inactivation of the contractile apparatus is brought about by a second enzyme, the myosin light chain phosphatase. There is considerable experimental evidence in support of the phosphorylation theory and it appears that it must be at least a part of the regulatory system. However, it cannot be concluded that phosphorylation-dephosphorylation of myosin is the sole regulatory mechanism, and recent results have indicated that additional factors may be involved. The second theory to account for the activation of the contractile apparatus is not based on the phosphorylation of the myosin molecule and is thought to be due to a system called leiotonin. This system, composed of two subunits leiotonin A and C, is thought to be associated with the thin filaments. Its mode of action has not been established.

          Related collections

          Author and article information

          Journal
          JVR
          J Vasc Res
          10.1159/issn.1018-1172
          Journal of Vascular Research
          S. Karger AG
          1018-1172
          1423-0135
          1982
          1982
          19 September 2008
          : 19
          : 1
          : 1-18
          Affiliations
          aMuscle Biology Group, Departments of Biochemistry and Nutrition and Food Science, University of Arizona, Tucson, Ariz., USA; bII. Physiologisches Institut, Heidelberg, BRD
          Article
          158369 Blood Vessels 1982;19:1–18
          10.1159/000158369
          © 1982 S. Karger AG, Basel

          Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

          Page count
          Pages: 18
          Categories
          Review

          Comments

          Comment on this article