Plasma membrane Ca(2+)-pump ATPase is not a substrate for cGMP-dependent protein kinase.
A plasma membrane Ca(2+)-pump ATPase preparation purified from porcine aorta was incubated with cGMP-dependent protein kinase (G-kinase) under the conditions under which dose-dependent stimulation of the enzyme by G-kinase was observed. Several proteins were phosphorylated, but two isoforms of plasma membrane Ca(2+)-pump ATPase with molecular masses of 135- and 145-kDa were not phosphorylated. The protein that was phosphorylated by G-kinase and identified in our previous study as the 135-kDa isoform of Ca(2+)-pump ATPase, on the basis of its almost identical mobility on SDS-PAGE, was found to be another protein with a molecular mass of 138 kDa. Fractionation of the enzyme preparation after incubation with G-kinase by a newly developed calmodulin affinity chromatographic method resulted in the separation of all the G-kinase substrates from the two isoforms of plasma membrane Ca(2+)-pump ATPase. These results suggest that the direct phosphorylation of the Ca(2+)-pump ATPase does not occur in association with the stimulation of the plasma membrane Ca(2+)-pump ATPase by G-kinase.
Yoshida
Y
Y
Department of Pharmacology, Niigata University School of Medicine.
Cai
J Q
JQ
Imai
S
S
D000818:Animals; D001011:Aorta / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D066298:In Vitro Techniques; D008970:Molecular Weight; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D013379:Substrate Specificity; D013552:Swine
D011494:Protein Kinases; D000252:Calcium-Transporting ATPases