-transparent.png){kind=logo}
Three proteins having Mr of 20 000, 35 000, and 57 000 were phosphorylated by a calmodulin-dependent system in fast skeletal muscle sarcoplasmic reticulum (SR). The 20 000-dalton phosphoprotein was an acidic proteolipid distinct from phospholamban, which was present in cardiac SR preparations. The 57 000-dalton phosphoprotein became phosphorylated very rapidly (t1/2 = 5-10 s at 0 degrees C) and was distinct from calsequestrin and the 53 000-dalton glycoprotein, as judged from the electrophoretic mobility on neutral Laemmli gels and from its detergent-extraction characteristics. None of the three phosphoproteins interacted directly with calmodulin, implying that they were not the regulatory subunit of the calmodulin-dependent kinase. The calmodulin-dependent kinase(s) responsible for the phosphorylation of the three protein substrates was (were) membrane bound. Its Km(ATP) was about 200 microM, and at the probable physiological calmodulin concentration of 1-2 microM, its Km (Ca) was 0.7 microM. The 57 000-dalton phosphoprotein was dephosphorylated by an endogenous phosphatase activity, which was also activated by the Ca-calmodulin complex.
M Chiesi, and
E Carafoli
September 1988,
The Journal of biological chemistry,
M Chiesi, and
E Carafoli
February 1988,
Biochimica et biophysica acta,
M Chiesi, and
E Carafoli
January 1994,
Biochemistry,
M Chiesi, and
E Carafoli
January 1984,
Advances in cyclic nucleotide and protein phosphorylation research,
M Chiesi, and
E Carafoli
January 1988,
Progress in clinical and biological research,
M Chiesi, and
E Carafoli
January 1986,
Biochemistry,
M Chiesi, and
E Carafoli
December 1999,
Acta physiologica Scandinavica,
M Chiesi, and
E Carafoli
May 2008,
American journal of physiology. Cell physiology,
M Chiesi, and
E Carafoli
August 1988,
FEBS letters,
M Chiesi, and
E Carafoli
February 1989,
Circulation research,
