Activation of sarcoplasmic reticular Ca2+ transport ATPase by phosphorylation of an associated phosphatidylinositol.
Approximately 1 mol phosphatidylinositol phosphate is formed per mol isolated Ca2+ transport ATPase when the enzyme is incubated with ATP/Mg2+. The phosphorylation of this enzyme-associated phosphatidylinositol represents the alkylphosphate formation described earlier. The phosphatidylinositol phosphate has been found in the hydrophobic core of the enzyme. A complex of phosphatidylinositol phosphate with protein can be extracted with acidic chloroform/methanol. The protein behaves like proteolipid during chromatography on Sephadex LH 60 and binds the radioactively labelled phosphatidylinositol phosphate. The phosphorylation of approximately 1 mol phosphatidylinositol per 100,000 g protein correlates with an enhancement of the Ca2+ transport ATPase activity which is due to an approximately 7-fold enhanced affinity for Ca2+ and an approximately 2-fold enhanced maximal turnover.
Varsanyi
M
M
Institut für Physiologische Chemie, Lehrstuhl I, Ruhr-Universität, Bochum, FRG.
Tölle
H G
HG
Heilmeyer
M G
MG
Dawson
R M
RM
Irvine
R F
RF
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002417:Cattle; D004789:Enzyme Activation; D066298:In Vitro Techniques; D007700:Kinetics; D018482:Muscle, Skeletal / Q000201:enzymology; D018129:Phosphatidylinositol Phosphates / Q000096:biosynthesis; D010716:Phosphatidylinositols / Q000378:metabolism*; D010766:Phosphorylation; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*
D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D000252:Calcium-Transporting ATPases