The actin ‘A-triad's’ role in contractile regulation in health and disease

William Schmidt, Anthony Cammarato

Research output: Contribution to journalReview articlepeer-review

4 Scopus citations


Striated muscle contraction is regulated by Ca2+-dependent modulation of myosin cross-bridge binding to F-actin by the thin filament troponin (Tn)-tropomyosin (Tm) complex. In the absence of Ca2+, 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. (Figure presented.).

Original languageEnglish (US)
Pages (from-to)2897-2908
Number of pages12
JournalJournal of Physiology
Issue number14
StatePublished - Jul 1 2020


  • acetylation
  • hypertrophic cardiomyopathy
  • muscle contraction
  • myosin
  • post-translational modifications
  • steric regulation
  • tropomyosin

ASJC Scopus subject areas

  • Physiology


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