Troponin, tripomyosin, and actin interactions in the Ca2+ ion regulation of muscle contraction

James D. Potter, John Gergely

Research output: Contribution to journalArticlepeer-review

211 Scopus citations


The effect of Ca2+ on the interaction of troponin (TN) and its components with F-actin, tropomyosin, and the F-actin-tropomyosin complex has been studied. The Cabinding component of TN (TN-C) did not bind to F-actin, F-actin-tropomyosin, or tropomyosin regardless of whether Ca2+ was present. A complex of TN-C and of the inhibitory component (TN-I) bound to F-actin only in the presence of tropomyosin and in the absence of Ca2+. TN-I was weakly bound to F-actin and more strongly to F-actin-tropomyosin. Unfractionated troponin bound tightly to tropomyosin and to F-actin-tropomyosin but only weakly to F-actin, and in both cases the binding was not affected by Ca2+. The tropomyosin-binding component of TN (TN-T) and a complex of TN-C and TN-T bound to tropomyosin and to F-actin-tropomyosin but not to F-actin alone. On the basis of these binding studies and the known positions of tropomyosin on the thin actin-containing filaments during contraction and relaxation, a model is proposed which may explain how troponin and Ca2+ regulate muscle contraction.

Original languageEnglish (US)
Pages (from-to)2697-2703
Number of pages7
Issue number13
StatePublished - Jun 1 1974

ASJC Scopus subject areas

  • Biochemistry


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