Abstract
S100, a subfamily of the EF-hand type calcium sensing proteins, is implicated in many cellular functions including muscle contractility. Two isoforms, S100A1 and S100B, at 2-10 microM significantly inhibit active tension, stiffness and ATPase of skinned single rabbit psoas muscle fibers at sub-maximal (pCa approximately 6.1-5.6), but not at maximal levels of activation (pCa 4.0). S100A1 is a more potent inhibitor than S100B. Hill analysis of the ATPase-pCa and tension-pCa curves indicates that these proteins reduce calcium sensitivity and enhance the cooperativity toward calcium. We propose S100A1, and perhaps S100B, are viable candidates as physiological modulators of muscle contraction.
MeSH terms
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Adenosine Triphosphatases / antagonists & inhibitors
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Adenosine Triphosphatases / metabolism*
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Animals
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Calcium / metabolism*
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Calcium / pharmacology
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Calcium-Binding Proteins / metabolism*
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Calcium-Binding Proteins / pharmacology
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Dose-Response Relationship, Drug
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In Vitro Techniques
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Isometric Contraction / drug effects
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Isometric Contraction / physiology
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Muscle Contraction / drug effects
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Muscle Contraction / physiology*
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Muscle Fibers, Skeletal / drug effects
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Muscle Fibers, Skeletal / metabolism
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Muscle Tonus / drug effects
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Muscle Tonus / physiology
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Muscle, Skeletal / drug effects
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Muscle, Skeletal / metabolism*
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Protein Isoforms / metabolism
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Protein Isoforms / pharmacology
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Rabbits
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S100 Proteins
Substances
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Calcium-Binding Proteins
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Protein Isoforms
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S100 Proteins
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S100A1 protein
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Adenosine Triphosphatases
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Calcium