Document Detail


The structural dynamics of actin during active interaction with myosin depends on the isoform of the essential light chain.
MedLine Citation:
PMID:  23339370     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We have used time-resolved phosphorescence anisotropy to investigate the effects of essential light chain (ELC) isoforms (A1 and A2) on the interaction of skeletal muscle myosin with actin, to relate structural dynamics to previously reported functional effects. Actin was labeled with a phosphorescent probe at C374, and the myosin head (S1) was separated into isoenzymes S1A1 and S1A2 by ion-exchange chromatography. As previously reported, S1A1 exhibited substantially lower ATPase activity at saturating actin concentrations but substantially higher apparent actin affinity, resulting in a higher catalytic efficiency. In the absence of ATP, each isoenzyme increased actin's final anisotropy cooperatively and to a similar extent, indicating a similar restriction of the amplitude of intrafilament rotational motions in the strong-binding (S) state of actomyosin. In contrast, in the presence of a saturating level of ATP, S1A1 increased actin anisotropy much more than S1A2 and with greater cooperativity, indicating that S1A1 was more effective in restricting actin dynamics during the active interaction of actin and myosin. We conclude that during the active interaction of actin and ATP with myosin, S1A1 is more effective at stabilizing the S state (probably the force-generating state) of actomyosin, while S1A2 tends to stabilize the weak-binding (non-force-generating) W state. When a mixture of isoenzymes is present, S1A1 is dominant in its effects on actin dynamics. We conclude that ELC of skeletal muscle myosin modulates strong-to-weak structural transitions during the actomyosin ATPase cycle in an isoform-dependent manner, with significant implications for the contractile function of actomyosin.
Authors:
Ewa Prochniewicz; Piyali Guhathakurta; David D Thomas
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2013-02-15
Journal Detail:
Title:  Biochemistry     Volume:  52     ISSN:  1520-4995     ISO Abbreviation:  Biochemistry     Publication Date:  2013 Mar 
Date Detail:
Created Date:  2013-03-05     Completed Date:  2013-04-22     Revised Date:  2013-07-11    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1622-30     Citation Subset:  IM    
Affiliation:
Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA.
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MeSH Terms
Descriptor/Qualifier:
Actins / analysis,  metabolism*
Actomyosin / analysis,  metabolism
Adenosine Triphosphatases / metabolism
Adenosine Triphosphate / metabolism
Animals
Anisotropy
Luminescent Agents / analysis
Luminescent Measurements
Models, Molecular
Muscle, Skeletal / chemistry,  metabolism
Myosin Light Chains / analysis,  metabolism*
Osmolar Concentration
Protein Isoforms / analysis,  metabolism
Rabbits
Grant Support
ID/Acronym/Agency:
AR32961/AR/NIAMS NIH HHS; AR57220/AR/NIAMS NIH HHS; R01 AG026160/AG/NIA NIH HHS; R01 AR032961/AR/NIAMS NIH HHS; R01 AR063007/AR/NIAMS NIH HHS; R37 AG026160/AG/NIA NIH HHS; T32 AR007612/AR/NIAMS NIH HHS; T32 AR007612/AR/NIAMS NIH HHS
Chemical
Reg. No./Substance:
0/Actins; 0/Luminescent Agents; 0/Myosin Light Chains; 0/Protein Isoforms; 56-65-5/Adenosine Triphosphate; 9013-26-7/Actomyosin; EC 3.6.1.-/Adenosine Triphosphatases
Comments/Corrections

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