You are not currently logged in.
Access JSTOR through your library or other institution:
If You Use a Screen ReaderThis content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Regulation of Myosin Filament Assembly by Light-Chain Phosphorylation [and Discussion]
R. C. Smith, W. Z. Cande, R. Craig, P. J. Tooth, J. M. Scholey, J. Kendrick-Jones and N. Crawford
Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
Vol. 302, No. 1108, Biological Roles of Protein Phosphorylation (Jul. 5, 1983), pp. 73-82
Published by: Royal Society
Stable URL: http://www.jstor.org/stable/2396043
Page Count: 12
You can always find the topics here!Topics: Phosphorylation, Gizzard, Molecules, Actins, Smooth muscle, Turbidity, Vertebrates, Monomers, Molecular chains, Muscles
Were these topics helpful?See somethings inaccurate? Let us know!
Select the topics that are inaccurate.
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Preview not available
Myosins isolated from vertebrate smooth muscles and non-muscle cells such as lymphocytes and platelets contain regulatory light chains (Mr = 20 000), which are phosphorylated by a Ca2+-calmodulin-dependent kinase and dephosphorylated by a Ca2+-insensitive phosphatase. Phosphorylation of the regulatory light chains of these myosins in vitro regulates not only their interactions with actin but also their assembly into filaments. Under approximately physiological conditions (0.15 M NaCl, pH 7.0) stoichiometric levels of Mg-ATP disassemble these non-phosphorylated myosin filaments into species with sedimentation coefficients (So 20,w) of approximately 11S. Hydrodynamic and electron microscope observations have indicated that this 11S species is a monomer with a folded conformation (Trybus et al., Proc. natn. Acad. Sci. U.S.A. 79, 6151 (1982)). Rotary shadowing reveals that the tails of disassembled gizzard and thymus myosins are folded twice at two hinge points to form a folded three-segment structure. Phosphorylation of the regulatory light chains of these myosins causes these folded 11S molecules to unfold into the conventional extended monomeric form (6S), which is able to assemble into filaments. Thus in vitro these myosin filaments can be assembled or disassembled by phosphorylation or dephosphorylation of their light chains. Whether these results have any relevance to the situation within living non-muscle and smooth muscle cells remains to be established.
Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences © 1983 Royal Society