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Related Experiment Videos

Phosphorylation of caldesmon.

J C Abougou1, M Hagiwara, T Hachiya

  • 1Muscle Biology Group, University of Arizona, Tucson 85721.

FEBS Letters
|November 6, 1989
PubMed
Summary
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Caldesmon phosphorylation was investigated to identify its kinase. Results indicate caldesmon is not a kinase; activity stems from calcium/calmodulin-dependent protein kinase II, not endogenous enzymes.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Signaling

Background:

  • Caldesmon is a protein involved in actin-binding and smooth muscle contraction.
  • Its phosphorylation by various kinases affects its function.
  • The source of endogenous kinase activity in caldesmon preparations was unclear.

Purpose of the Study:

  • To determine if caldesmon itself possesses kinase activity.
  • To identify the specific kinase responsible for caldesmon phosphorylation in cellular preparations.
  • To elucidate the role of calcium and calmodulin in regulating kinase activity associated with caldesmon.

Main Methods:

  • Studying the phosphorylation of caldesmon.
  • Titrating kinase activity with varying ratios of calmodulin to caldesmon.

Related Experiment Videos

  • Comparing phosphorylation sites by calcium/calmodulin-dependent protein kinase II, endogenous kinase, and protein kinase C.
  • Assessing changes in endogenous kinase activity following phosphorylation in the presence and absence of Ca2+ and calmodulin.

    • Main Results:

    • Kinase activity showed maximum levels at substoichiometric ratios of calmodulin/caldesmon.
    • Phosphorylation sites for calcium/calmodulin-dependent protein kinase II and the endogenous kinase were identical.
    • These sites differed from those phosphorylated by protein kinase C.
    • Pre-phosphorylation with Ca2+ and calmodulin enhanced subsequent endogenous kinase activity without Ca2+.

    Conclusions:

    • Caldesmon does not exhibit intrinsic protein kinase activity.
    • The observed kinase activity in caldesmon preparations is attributed to calcium/calmodulin-dependent protein kinase II.
    • Calcium and calmodulin play a regulatory role in the activity of this associated kinase.