KINETICS OF CALCIUM AND CALMODULIN-DEPENDENT PROTEIN-KINASE-III FROM EMBRYONIC CHICKEN LEG MUSCLE-CELLS

Embryonic chicken muscle cells (CELM) contain the calmodulin-dependent protein kinase that specifically phosphorylates eukaryotic elongation factor 2, The kinase requires Ca2+ and maximum activity in CELM was o bserved at 10 mu M Ca2+. The ATP concentration required for half the m aximum activity of CaM PKIII in CELM was calculated to be 0.15 mM. In CELM, dephosphorylation of eEF-2 was catalyzed by phosphoprotein phosp hatase PP2A alone. The activity of PP2A was relatively low and the hal f-life of added phosphorylated eEF-2 was more than 15 min, Due to the low phosphoprotein phosphatase activity, inhibition of the PP2A activi ty by addition of okadaic acid had little effect on the eEF-2 phosphor ylation kinetics. (C) 1997 Federation of European Biochemical Societie s.