Effect of phosphorylation of porcine cardiac troponin I by 3': 5'-cyclic AMP-dependent protein kinase on the actomyosin ATPase activity

Kazuhiko Yamamoto, Iwao Ohtsuki

Research output: Contribution to journalArticle

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Abstract

1. Porcine cardiac native tropomyosin was phosphorylated by bovine cardiac 3': 5'-cyclic AMP-dependent protein kinase. Most of the phosphate incorporation was observed in troponin I, the maximum of which was 0.7 mol of P1 per mol of troponin I.2. In the presence of phosphorylated native tropomyosin, actomyosin ATPase activity was 15-40% lower than that in the presence of the unphosphorylated preparation at all calcium ion concentrations (1.5 × 10-8 M-2.4 × 10-5 M). Half-maximum activation of ATPase was obtained with a concentration of 7 × 10-7 M Ca2+ (unphosphorylated) and 1.3 × 10-6 M Ca2+ (phosphorylated), respectively. Maximum ATPase activity was reached with 3 × 10-6 M Ca2+ (unphosphorylated) and 1.0 × 10-5 M Ca2+ (phosphorylated).3. Porcine cardiac troponin I isolated by affinity chromatography inhibited ATPase activity of desensitized actomyosin in the presence of tropomyosin. There was little difference between phosphorylated troponin I and a control preparation with regard to the inhibitory effect on ATPase activity.4. Troponin C from rabbit skeletal muscle neutralized the inhibitory effect of troponin I. The minimum amount of troponin C required for complete neutralization was approximately equimolar to troponin I. The inhibitory effect of phosphorylated troponin I was neutralized by troponin C less effectively than that of unphosphorylated preparation.

Original languageEnglish
Pages (from-to)1669-1677
Number of pages9
JournalJournal of biochemistry
Volume91
Issue number5
DOIs
Publication statusPublished - Apr 1982

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Phosphorylation
Troponin I
Myosins
Cyclic AMP-Dependent Protein Kinases
Swine
Troponin C
Tropomyosin
Adenosine Triphosphatases
Affinity chromatography
Actomyosin
Troponin
Affinity Chromatography
Muscle
Skeletal Muscle
Chemical activation
Phosphates
Ions
Rabbits
Calcium

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology

Cite this

Effect of phosphorylation of porcine cardiac troponin I by 3' : 5'-cyclic AMP-dependent protein kinase on the actomyosin ATPase activity. / Yamamoto, Kazuhiko; Ohtsuki, Iwao.

In: Journal of biochemistry, Vol. 91, No. 5, 04.1982, p. 1669-1677.

Research output: Contribution to journalArticle

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abstract = "1. Porcine cardiac native tropomyosin was phosphorylated by bovine cardiac 3': 5'-cyclic AMP-dependent protein kinase. Most of the phosphate incorporation was observed in troponin I, the maximum of which was 0.7 mol of P1 per mol of troponin I.2. In the presence of phosphorylated native tropomyosin, actomyosin ATPase activity was 15-40{\%} lower than that in the presence of the unphosphorylated preparation at all calcium ion concentrations (1.5 × 10-8 M-2.4 × 10-5 M). Half-maximum activation of ATPase was obtained with a concentration of 7 × 10-7 M Ca2+ (unphosphorylated) and 1.3 × 10-6 M Ca2+ (phosphorylated), respectively. Maximum ATPase activity was reached with 3 × 10-6 M Ca2+ (unphosphorylated) and 1.0 × 10-5 M Ca2+ (phosphorylated).3. Porcine cardiac troponin I isolated by affinity chromatography inhibited ATPase activity of desensitized actomyosin in the presence of tropomyosin. There was little difference between phosphorylated troponin I and a control preparation with regard to the inhibitory effect on ATPase activity.4. Troponin C from rabbit skeletal muscle neutralized the inhibitory effect of troponin I. The minimum amount of troponin C required for complete neutralization was approximately equimolar to troponin I. The inhibitory effect of phosphorylated troponin I was neutralized by troponin C less effectively than that of unphosphorylated preparation.",
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N2 - 1. Porcine cardiac native tropomyosin was phosphorylated by bovine cardiac 3': 5'-cyclic AMP-dependent protein kinase. Most of the phosphate incorporation was observed in troponin I, the maximum of which was 0.7 mol of P1 per mol of troponin I.2. In the presence of phosphorylated native tropomyosin, actomyosin ATPase activity was 15-40% lower than that in the presence of the unphosphorylated preparation at all calcium ion concentrations (1.5 × 10-8 M-2.4 × 10-5 M). Half-maximum activation of ATPase was obtained with a concentration of 7 × 10-7 M Ca2+ (unphosphorylated) and 1.3 × 10-6 M Ca2+ (phosphorylated), respectively. Maximum ATPase activity was reached with 3 × 10-6 M Ca2+ (unphosphorylated) and 1.0 × 10-5 M Ca2+ (phosphorylated).3. Porcine cardiac troponin I isolated by affinity chromatography inhibited ATPase activity of desensitized actomyosin in the presence of tropomyosin. There was little difference between phosphorylated troponin I and a control preparation with regard to the inhibitory effect on ATPase activity.4. Troponin C from rabbit skeletal muscle neutralized the inhibitory effect of troponin I. The minimum amount of troponin C required for complete neutralization was approximately equimolar to troponin I. The inhibitory effect of phosphorylated troponin I was neutralized by troponin C less effectively than that of unphosphorylated preparation.

AB - 1. Porcine cardiac native tropomyosin was phosphorylated by bovine cardiac 3': 5'-cyclic AMP-dependent protein kinase. Most of the phosphate incorporation was observed in troponin I, the maximum of which was 0.7 mol of P1 per mol of troponin I.2. In the presence of phosphorylated native tropomyosin, actomyosin ATPase activity was 15-40% lower than that in the presence of the unphosphorylated preparation at all calcium ion concentrations (1.5 × 10-8 M-2.4 × 10-5 M). Half-maximum activation of ATPase was obtained with a concentration of 7 × 10-7 M Ca2+ (unphosphorylated) and 1.3 × 10-6 M Ca2+ (phosphorylated), respectively. Maximum ATPase activity was reached with 3 × 10-6 M Ca2+ (unphosphorylated) and 1.0 × 10-5 M Ca2+ (phosphorylated).3. Porcine cardiac troponin I isolated by affinity chromatography inhibited ATPase activity of desensitized actomyosin in the presence of tropomyosin. There was little difference between phosphorylated troponin I and a control preparation with regard to the inhibitory effect on ATPase activity.4. Troponin C from rabbit skeletal muscle neutralized the inhibitory effect of troponin I. The minimum amount of troponin C required for complete neutralization was approximately equimolar to troponin I. The inhibitory effect of phosphorylated troponin I was neutralized by troponin C less effectively than that of unphosphorylated preparation.

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