Ca2+ binding to skeletal muscle troponin C in skeletal and cardiac myofibrils

Sachio Morimoto, Iwao Ohtsuki

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Ca2+ binding to skeletal muscle troponin C in skeletal or cardiac myofibrils was measured by the centrifugation method using 45Ca. The specific Ca2+ binding to troponin C was obtained by subtracting the amount of Ca2+ bound to the CDTA-treated myofibrils (troponin C-depleted myofibrils) from that to the myofibrils reconstituted with troponin C. Results of Ca2+ binding measurement at various Ca2+ concentrations showed that skeletal troponin C had two classes of binding sites with different affinity for Ca2+. The Ca2+ binding of low-affinity sites in cardiac myofibrils was about eight times lower than that in skeletal myofibrils, while the high-affinity sites of troponin C in skeletal or cardiac myofibrils showed almost the same affinity for Ca2+. The Ca2+ sensitivity of the ATPase activity of skeletal troponin C-reconstituted cardiac myofibrils was also about eight times lower than that of skeletal myofibrils reconstituted with troponin C. These findings indicated that the difference in the sensitivity to Ca2+ of the ATPase activity between skeletal and cardiac CDTA-treated myofibrils reconstituted with skeletal troponin C was mostly due to the change in the affinity for Ca2+ of the low-affinity sites on the C troponin C molecule.

Original languageEnglish
Pages (from-to)435-439
Number of pages5
JournalJournal of biochemistry
Volume105
Issue number3
DOIs
Publication statusPublished - Mar 1989

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology

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