What question did this study set out to answer?

To determine how myosin light-chain phosphorylation, calcium ions, and tropomyosin regulate the actin-activated ATPase activity of mammalian smooth muscle myosin.

February 17, 1981Biochemistry

Effects of phosphorylation, calcium ion, and tropomyosin on actin-activated adenosine 5'-triphosphatase activity of mammalian smooth muscle myosin

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Population

Actomyosin isolated from bovine stomach muscle and rabbit skeletal muscle actin

Comparison

Phosphorylation of the 20,000-dalton light… vs Unphosphorylated myosin, absence of calcium, and…

Design

Preclinical

Authors

SCSamuel ChackoAmrita Institute of Medical Sciences and Research Centre

Discussion

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Implication

Provides mechanistic insight into smooth muscle regulation; leaves open translation to human physiology or therapy.

Key Points

To determine how myosin light-chain phosphorylation, calcium ions, and tropomyosin regulate the actin-activated ATPase activity of mammalian smooth muscle myosin.
Purified myosin from bovine stomach muscle actomyosin via gel filtration on a Sepharose 4B-agarose column following phosphorylation or dephosphorylation by endogenous enzymes.
Assayed actin-activated ATPase activity using purified rabbit skeletal muscle actin and tropomyosin across varying calcium concentrations and protein molar ratios.
Actin activated myosin ATPase activity only when the 20,000-dalton light chain was phosphorylated, reaching peak activation at a 1:20 myosin-to-actin molar ratio.
Once myosin was phosphorylated and isolated from kinase and phosphatase activity, actin-activated ATPase activity operated independently of calcium ion concentration.
Complexing actin with tropomyosin at a 1:6 molar ratio potentiated ATP hydrolysis to its highest level in fully phosphorylated myosin, also occurring independently of calcium.

Structured PICO

Population

Actomyosin isolated from bovine stomach muscle and rabbit skeletal muscle actin

Intervention

Phosphorylation of the 20,000-dalton light chain, addition of calcium ions, and complexing actin with tropomyosin

Comparator

Unphosphorylated myosin, absence of calcium, and absence of tropomyosin

Outcome

Actin-activated adenosine 5'-triphosphatase (ATPase) activitysurrogate

Tropomyosin significantly potentiates actin-activated ATP hydrolysis by smooth muscle myosin independent of calcium, provided the myosin light chain is phosphorylated.

Cite This Study

Samuel Chacko (1981) studied this question.

synapsesocial.com/papers/6a7d16e92935e92dbc775556 https://doi.org/10.1021/bi00507a005

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Effects of phosphorylation, calcium ion, and tropomyosin on actin-activated adenosine 5'-triphosphatase activity of mammalian smooth muscle myosin

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Effects of phosphorylation, calcium ion, and tropomyosin on actin-activated adenosine 5'-triphosphatase activity of mammalian smooth muscle myosin

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

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