Document Detail

Structural and functional responses of mammalian thick filaments to alterations in myosin regulatory light chains.
MedLine Citation:
PMID:  9724616     Owner:  NLM     Status:  MEDLINE    
The ordered array of myosin heads, characteristic of relaxed striated muscle thick filaments, is reversibly disordered by phosphorylating myosin regulatory light chains, decreasing temperature and/or ionic strength, increasing pH, and depleting nucleotide. In the case of light chain phosphorylation, disorder, most likely due to a change in charge affecting the light chain amino-terminus, reflects increased myosin head mobility, thus increased accessibility to actin, and results in increased calcium sensitivity of tension development. Thus, interactions between the unphosphorylated regulatory light chain and the filament backbone may help maintain the overall order of the relaxed filament. To define this relationship, we have examined the structural and functional effects of such manipulations as exchanging wild-type smooth and skeletal myosin light chains into permeabilized rabbit psoas fibers and removing regulatory light chains (without exchange) from such fibers. We have also compared the structural and functional parameters of biopsied fibers from patients with severe familial hypertrophic cardiomyopathy due to a single amino acid substitution in the regulatory light chains to those exhibited by fibers from normal relatives. Our results support a role for regulatory light chains in reversible ordering of myosin heads and suggest that economy of energy utilization may provide for evolutionary preservation of this function in vertebrate striated muscle.
R J Levine; Z Yang; N D Epstein; L Fananapazir; J T Stull; H L Sweeney
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of structural biology     Volume:  122     ISSN:  1047-8477     ISO Abbreviation:  J. Struct. Biol.     Publication Date:  1998  
Date Detail:
Created Date:  1998-10-29     Completed Date:  1998-10-29     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  9011206     Medline TA:  J Struct Biol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  149-61     Citation Subset:  IM; S    
Copyright Information:
Copyright 1998 Academic Press.
Department of Neurobiology and Anatomy, MCPdiamondHahnemann School of Medicine, Allegheny University of the Health Sciences, 3200 Henry Avenue, Philadelphia, Pennsylvania, 19129, USA.
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MeSH Terms
Amino Acid Sequence
Amino Acid Substitution
Cardiomyopathy, Hypertrophic / genetics
Cell Membrane Permeability
Microfilaments / ultrastructure*
Microscopy, Electron
Molecular Sequence Data
Muscle Fibers, Skeletal / metabolism*,  ultrastructure
Muscle Fibers, Slow-Twitch / ultrastructure
Muscle, Skeletal / metabolism
Myosin Light Chains / genetics,  metabolism*
Structure-Activity Relationship
Grant Support
Reg. No./Substance:
0/Myosin Light Chains

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