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The actin ‘A‐triad's’ role in contractile regulation in health and disease
Author(s) -
Schmidt William,
Cammarato Anthony
Publication year - 2019
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jp276741
Subject(s) - actin , tropomyosin , myosin , biophysics , chemistry , troponin , muscle contraction , muscle relaxation , protein filament , microbiology and biotechnology , actin binding protein , actin cytoskeleton , biochemistry , biology , anatomy , cytoskeleton , medicine , cell , endocrinology , myocardial infarction
Striated muscle contraction is regulated by Ca 2+ ‐dependent modulation of myosin cross‐bridge binding to F‐actin by the thin filament troponin (Tn)‐tropomyosin (Tm) complex. In the absence of Ca 2+ , Tn binds to actin and constrains Tm to an azimuthal location where it sterically occludes myosin binding sites along the thin filament surface. This limits force production and promotes muscle relaxation. In addition to Tn‐actin interactions, inhibitory Tm positioning requires associations between other thin filament constituents. For example, the actin ‘A‐triad’, composed of residues K326, K328 and R147, forms numerous, highly favourable electrostatic contacts with Tm that are critical for establishing its inhibitory azimuthal binding position. Here, we review recent findings, including the identification and interrogation of modifications within and proximal to the A‐triad that are associated with disease and/or altered muscle behaviour, which highlight the surface feature's role in F‐actin‐Tm interactions and contractile regulation.