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| The EMBO Journal
(1997) 16, 211–220, doi:10.1093/emboj/16.2.211 |
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| Molecular structure of the sarcomeric M band: mapping of titin and myosin binding domains in myomesin and the identification of a potential regulatory phosphorylation site in myomesin |
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| Wolfgang M.J. Obermann1, Mathias Gautel2, Klaus Weber1 and Dieter O. Fürst1, 3 |
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1 Max-Planck-Institute for Biophysical Chemistry, Department of Biochemistry, PO Box 2841, D-37077 Göttingen, Germany 2 European Molecular Biology Laboratory, Biological Structures and Biocomputing Program, D-69012 Heidelberg, Germany 3 University of Potsdam, Department of Cell Biology, Lennéstrasse 7a, D-14471 Potsdam, Germany Received 1 August 1996; Revised 30 September 1996. |
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| Abstract |
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| The M band of sarcomeric muscle is a highly complex structure which contributes to the maintenance of the regular lattice of thick filaments. We propose that the spatial coordination of this assembly is regulated by specific interactions of myosin filaments, the M band protein myomesin and the large carboxy-terminal region of titin. Corresponding binding sites between these proteins were identified. Myomesin binds myosin in the central region of light meromyosin (LMM, myosin residues 1506–1674) by its unique amino-terminal domain My1. A single titin immunoglobulin domain, m4, interacts with a myomesin fragment spanning domains My4–My6. This interaction is regulated by phosphorylation of Ser482 in the linker between myomesin domains My4 and My5. Myomesin phosphorylation at this site by cAMP-dependent kinase and similar or identical activities in muscle extracts block the association with titin. We propose that this demonstration of a phosphorylation-controlled interaction in the sarcomeric cytoskeleton is of potential relevance for sarcomere formation and/or turnover. It also reveals how binding affinities of modular proteins can be regulated by modifications of inter-domain linkers. |
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| Keywords: myomesin, myosin binding, phosphorylation, sarcomere, titin binding |
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