title: A model for the phosphorylation of the Ca2+ + Mg2+-activated ATPase by phosphate.
abstract: We have shown that changes in fluorescence intensity for the Ca2+ + Mg2+-activated ATPase of sarcoplasmic reticulum labelled with fluorescein isothiocyanate following the addition of Ca2+ can give the ratio of the two conformations (E1 and E2) of the ATPase. We show that the fluorescence response to Ca2+ is unaffected by Mg2+, phosphate or K+, implying that these ions bind equally well to the E1 and E2 conformations. A model is presented for phosphorylation of the ATPase by phosphate as a function of pH, Mg2+, K+ and Ca2+.
mesh_terms: D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D016650:Fluorescein-5-isothiocyanate; D005452:Fluoresceins; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008954:Models, Biological; D010710:Phosphates / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000494:pharmacology; D011487:Protein Conformation / Q000187:drug effects; D013861:Thiocyanates; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology
chemical_list: D005452:Fluoresceins; D010710:Phosphates; D013861:Thiocyanates; D014639:Vanadium; D014638:Vanadates; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D016650:Fluorescein-5-isothiocyanate; D008274:Magnesium; D011188:Potassium; D002118:Calcium