Phosphorylation of troponin and myosin light chain by cAMP-independent casein kinase-2 from rabbit skeletal muscle

Toolsee J. Singh, Akira Akatsuka, Kathleen R. Blake, Kuo Ping Huang

Research output: Contribution to journalArticle

Abstract

Casein kinase-2 from rabbit skeletal muscle was found to phosphorylate, in addition to glycogen synthase, troponin from skeletal muscle, and myosin light chain from smooth muscle. Troponin T and the 20,000 Mr myosin light chain are phosphorylated by casein kinase-2 at much greater rates than glycogen synthase. The V values for the phosphorylation of troponin and myosin light chain are nearly an order of magnitude greater than that of glycogen synthase; however, the Km values for these two substrates are greater than that for glycogen synthase. The kinase activities with the various protein substrates are stimulated approximately three- and fivefold by 5 mm spermidine and 3 mm spermine, respectively. Heparin is a potent inhibitor of the kinase when casein, glycogen synthase, or myosin light chain is the substrate. However, with troponin as substrate the kinase is relatively insensitive to inhibition by heparin. The amount of heparin required for 50% inhibition with troponin as substrate is at least 10 times greater than with casein as substrate. The phosphorylation of troponin by casein kinase-2 results in the incorporation of phosphate into two major tryptic peptides, which are different from those phosphorylated by casein kinase-1. The site in myosin light chain phosphorylated by casein kinase-2 is different from that phosphorylated by myosin light chain kinase.

Original languageEnglish (US)
Pages (from-to)615-622
Number of pages8
JournalArchives of Biochemistry and Biophysics
Volume220
Issue number2
DOIs
StatePublished - Feb 1 1983

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology

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