Document Detail


Role of magnesium binding to myosin in controlling the state of cross-bridges in skeletal rabbit muscle.
MedLine Citation:
PMID:  6685530     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The effect of Mg2+ on the disposition of myosin cross-bridges was studied on myofibrils and synthetic myosin and rod filaments by employing chymotryptic digestion and chemical cross-linking methods. In the presence of low Mg2+ concentrations (0.1 mM), the proteolytic susceptibility at the heavy meromyosin/light meromyosin (HMM/LMM) junction in these three systems sharply increases over the pH range from 7.0 to 8.2. Such a change has been previously associated with the release of myosin cross-bridges from the filament surface [Ueno, H., & Harrington, W.F. (1981) J. Mol. Biol. 149, 619-640]. Millimolar concentrations of Mg2+ block or reverse this charge-dependent transition. Rod filaments show the same behavior as myosin filaments, indicating that the low-affinity binding sites for Mg2+ are located on the rod portion of myosin. The interpretation of these results in terms of Mg2+-mediated binding of cross-bridges to the filament backbone is supported by cross-linking experiments. The normalized rate of S-2 cross-linking in rod filaments at pH 8.0, kS-2/kLMM, increases upon addition of Mg2+ from 0.30 to 0.65 and approaches the cross-linking rate measured at pH 7.0 (0.75), when the cross-bridges are close to the filament surface. In rod filaments prepared from oxidized rod particles, chymotryptic digestion proceeds both at the S-2/LMM junction and at a new cleavage site located in the N-terminal portion of the molecule. Kinetic analysis of digestion rates at these two sites reveals that binding of Mg2+ to oxidized myosin rods has a similar effect at both sites over the pH range from 7.0 to 8.0.(ABSTRACT TRUNCATED AT 250 WORDS)
Authors:
E Reisler; J Liu; P Cheung
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biochemistry     Volume:  22     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  1983 Oct 
Date Detail:
Created Date:  1984-01-27     Completed Date:  1984-01-27     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  4954-60     Citation Subset:  IM; S    
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MeSH Terms
Descriptor/Qualifier:
Animals
Chymotrypsin
Cytoskeleton / drug effects,  ultrastructure
Hydrogen-Ion Concentration
Kinetics
Magnesium / pharmacology*
Muscles / metabolism*
Myofibrils / drug effects,  ultrastructure*
Myosins / isolation & purification,  metabolism*
Peptide Fragments / analysis
Rabbits
Grant Support
ID/Acronym/Agency:
AM 22031/AM/NIADDK NIH HHS
Chemical
Reg. No./Substance:
0/Peptide Fragments; 7439-95-4/Magnesium; EC 3.4.21.1/Chymotrypsin; EC 3.6.4.1/Myosins

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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