The effect of di- and trivalent cations on the phosphorylation of the Ca2+-ATPase in sarcoplasmic reticulum vesicles

• Published in: Biochimica et biophysica acta Vol. 817; no. 1; pp. 1 - 6
• Main Authors: DOMONKOS, J, HEINER, L, VARGHA, M. JR
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 11.07.1985; North-Holland
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Calcium - pharmacology; Calcium-Transporting ATPases - metabolism; Cations; Cations, Divalent; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Hydrolases; Hydroxylamine; Hydroxylamines - pharmacology; Kinetics; Lanthanum - pharmacology; Magnesium - pharmacology; Muscles - enzymology; Phosphorylation; Rabbits; Sarcoplasmic Reticulum - enzymology; Ca-ATPase; Phosphorylation; Enzyme; Ca,Mg-ATPase; Rabbit; Lagomorpha; Calcium Ions; Vertebrata; Mammalia; Sarcoplasmic reticulum; Lanthanum III Ions; Magnesium Ions; Cations
• ISSN: 0006-3002; 1878-2434

The steady-state level of phosphorylated intermediate (EP) of (Mg2+ + Ca2+)-ATPase is influenced by magnesium and calcium concentration in the Ca2+-transporting system of sarcoplasmic reticulum vesicles. At micromolar [Ca2+], the level of EP is increased by Mg2+, depending on its concentration. The effect of Mg2+ is less pronounced at lower Ca2+ concentration. At low [Mg2+], the EP formation increases at millimolar concentrations of Ca2+, suggesting, in accordance with earlier results, that the substrate may also be CaATP instead of MgATP. LaCl3 (1 mM) enhanced the EP formation at low Mg2+ concentration. Surprisingly, 10 microM LaCl3 caused a marked decrease in EP formation at high [Mg2+] and had little or no effect on the level of EP at low Mg2+ concentration. The inducing effect of 1 mM LaCl3 on the EP formation at low [Mg2+] and the inhibitory effect of 10 microM LaCl3 at high Mg2+ concentration draw attention to the involvement of divalent cation-binding sites with different affinity in phosphorylation and to the particular role of Mg2+ in the EP formation and EP decomposition.