The phosphorylation of troponin B by phosphorylase b kinase in skeletal muscle of mice carrying the phosphorylase b kinase deficiency gene

Gross, S.R.; Mayer, S.E.

Biochemical and Biophysical Research Communications 54(2): 823-830

1973


ISSN/ISBN: 0006-291X
PMID: 4356986
DOI: 10.1016/0006-291x(73)91498-8
Accession: 027693885

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Abstract
In skeletal muscle of animals with the phosphorylase b kinase deficiency gene there is < 1% of the normal activity to convert phosphorylase b to a in the presence of Ca++, Mg++, and ATP (1). Correspondingly, there is < 1% of the normal activity to phosphorylate phosphorylase b. Nevertheless, under the same conditions, these extracts catalyze the phosphorylation of troponin at a rate 57% of normal. Phosphorylase b converting activity can be sedimented from skeletal muscle of control mice by centrifugation. This fraction isolated from I strain skeletal muscle extracts phosphorylates troponin at a rate 29–39% of the control. EGTA1 (15 mM) inhibits troponin phosphorylation by 50–60% in this fraction from both strains. The EGTA inhibition is reversed by 15 mM Ca++. Thus the phosphorylase b kinase in skeletal muscle of animals with the phosphorylase b kinase deficiency gene can phosphorylate troponin B, although it shows little or no activity with phosphorylase as a substrate. This observation is consistent with the normal muscle contractility of I strain animals.