Ca2+- and Sr2+-sensitivity of the ATPase activity of rabbit skeletal myofibrils

Effect of the complete substitution of troponin C with cardiac troponin C, calmodulin, and parvalbumins

Sachio Morimoto, Iwao Ohtsuki

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64 Citations (Scopus)

Abstract

The Ca2+-sensitive ATPase activity of rabbit skeletal myofibrils disappeared completely after treatment with a solution containing CDTA, a strong divalent cation chelator, at a low ionic strength. A gel electrophoretic study revealed that all troponin C and about half of myosin light chain 2 were removed from the myofibrils by the CDTA treatment. The CDTA-treated myofibrils, when reconstituted with skeletal troponin C, showed almost exactly the same Ca2+- or Sr2+-sensitive ATPase activity as that of intact myofibrils. The CDTA-treated myofibrils reconstituted with porcine cardiac troponin C showed the same Ca2+- or Sr2+-sensitive of the ATPase as that of porcine cardiac myofibrils; Sr2+-sensitivity relative to Ca2+-sensitivity was about ten times higher than, and the maximal slope of the activation curve was about half that of skeletal myofibrils. These findings indicate that these characteristic features of divalent cation regulation in the contraction of skeletal and cardiac muscles are determined solely by the species of troponin C. Bovine brain calmodulin hardly activated the ATPase activity of the CDTA-treated myofibrils even in the presence of Ca2+. Excess calmodulin, however, was found to give Ca2+- or Sr2+-sensitivity to the ATPase activity of the CDTA-treated myofibrils. Frog skeletal parvalbumins 1 and 2, even in excess, did not affect the ATPase activity of the CDTA-treated myofibrils.

Original languageEnglish
Pages (from-to)291-301
Number of pages11
JournalJournal of biochemistry
Volume101
Issue number2
DOIs
Publication statusPublished - Jan 1 1987

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Troponin C
Parvalbumins
Myofibrils
Calmodulin
Adenosine Triphosphatases
Substitution reactions
Rabbits
Divalent Cations
Swine
Chelating Agents
CDTA
Ionic strength
Muscle
Brain
Calcium-Transporting ATPases
Gels
Chemical activation
Anura
Osmolar Concentration
Myocardium

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology

Cite this

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title = "Ca2+- and Sr2+-sensitivity of the ATPase activity of rabbit skeletal myofibrils: Effect of the complete substitution of troponin C with cardiac troponin C, calmodulin, and parvalbumins",
abstract = "The Ca2+-sensitive ATPase activity of rabbit skeletal myofibrils disappeared completely after treatment with a solution containing CDTA, a strong divalent cation chelator, at a low ionic strength. A gel electrophoretic study revealed that all troponin C and about half of myosin light chain 2 were removed from the myofibrils by the CDTA treatment. The CDTA-treated myofibrils, when reconstituted with skeletal troponin C, showed almost exactly the same Ca2+- or Sr2+-sensitive ATPase activity as that of intact myofibrils. The CDTA-treated myofibrils reconstituted with porcine cardiac troponin C showed the same Ca2+- or Sr2+-sensitive of the ATPase as that of porcine cardiac myofibrils; Sr2+-sensitivity relative to Ca2+-sensitivity was about ten times higher than, and the maximal slope of the activation curve was about half that of skeletal myofibrils. These findings indicate that these characteristic features of divalent cation regulation in the contraction of skeletal and cardiac muscles are determined solely by the species of troponin C. Bovine brain calmodulin hardly activated the ATPase activity of the CDTA-treated myofibrils even in the presence of Ca2+. Excess calmodulin, however, was found to give Ca2+- or Sr2+-sensitivity to the ATPase activity of the CDTA-treated myofibrils. Frog skeletal parvalbumins 1 and 2, even in excess, did not affect the ATPase activity of the CDTA-treated myofibrils.",
author = "Sachio Morimoto and Iwao Ohtsuki",
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T1 - Ca2+- and Sr2+-sensitivity of the ATPase activity of rabbit skeletal myofibrils

T2 - Effect of the complete substitution of troponin C with cardiac troponin C, calmodulin, and parvalbumins

AU - Morimoto, Sachio

AU - Ohtsuki, Iwao

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N2 - The Ca2+-sensitive ATPase activity of rabbit skeletal myofibrils disappeared completely after treatment with a solution containing CDTA, a strong divalent cation chelator, at a low ionic strength. A gel electrophoretic study revealed that all troponin C and about half of myosin light chain 2 were removed from the myofibrils by the CDTA treatment. The CDTA-treated myofibrils, when reconstituted with skeletal troponin C, showed almost exactly the same Ca2+- or Sr2+-sensitive ATPase activity as that of intact myofibrils. The CDTA-treated myofibrils reconstituted with porcine cardiac troponin C showed the same Ca2+- or Sr2+-sensitive of the ATPase as that of porcine cardiac myofibrils; Sr2+-sensitivity relative to Ca2+-sensitivity was about ten times higher than, and the maximal slope of the activation curve was about half that of skeletal myofibrils. These findings indicate that these characteristic features of divalent cation regulation in the contraction of skeletal and cardiac muscles are determined solely by the species of troponin C. Bovine brain calmodulin hardly activated the ATPase activity of the CDTA-treated myofibrils even in the presence of Ca2+. Excess calmodulin, however, was found to give Ca2+- or Sr2+-sensitivity to the ATPase activity of the CDTA-treated myofibrils. Frog skeletal parvalbumins 1 and 2, even in excess, did not affect the ATPase activity of the CDTA-treated myofibrils.

AB - The Ca2+-sensitive ATPase activity of rabbit skeletal myofibrils disappeared completely after treatment with a solution containing CDTA, a strong divalent cation chelator, at a low ionic strength. A gel electrophoretic study revealed that all troponin C and about half of myosin light chain 2 were removed from the myofibrils by the CDTA treatment. The CDTA-treated myofibrils, when reconstituted with skeletal troponin C, showed almost exactly the same Ca2+- or Sr2+-sensitive ATPase activity as that of intact myofibrils. The CDTA-treated myofibrils reconstituted with porcine cardiac troponin C showed the same Ca2+- or Sr2+-sensitive of the ATPase as that of porcine cardiac myofibrils; Sr2+-sensitivity relative to Ca2+-sensitivity was about ten times higher than, and the maximal slope of the activation curve was about half that of skeletal myofibrils. These findings indicate that these characteristic features of divalent cation regulation in the contraction of skeletal and cardiac muscles are determined solely by the species of troponin C. Bovine brain calmodulin hardly activated the ATPase activity of the CDTA-treated myofibrils even in the presence of Ca2+. Excess calmodulin, however, was found to give Ca2+- or Sr2+-sensitivity to the ATPase activity of the CDTA-treated myofibrils. Frog skeletal parvalbumins 1 and 2, even in excess, did not affect the ATPase activity of the CDTA-treated myofibrils.

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