Mg(2+)-ADP protects against inactivation of sarcoplasmic reticulum Ca2+,Mg(2+)-ATPase by N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl) carbodiimide.
N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl) carbodiimide (NCD-4) inactivates the sarcoplasmic reticulum Ca(2+)-ATPase by covalent labelling at or near the high affinity (transport) Ca2+ sites. Mg(2+)-ADP protects against the inactivation of the Ca(2+)-ATPase produced by NCD-4, with a K0.5 of Mg(2+)-ADP of 28 +/- 6 microM for purified Ca(2+)-ATPase. With native and solubilized sarcoplasmic reticulum membranes millimolar Mg(2+)-ADP concentrations are needed to produce an effective protection of the Ca(2+)-ATPase against inactivation by NCD-4. These results suggest a tight structural interconnection between catalytic and transport Ca2+ sites in the Ca(2+)-ATPase, modulated by protein-protein interactions in the SR membrane.
Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain.
J M
JM
Merino
C
C
Gutiérrez-Merino
D000244:Adenosine Diphosphate / Q000494:pharmacology*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002234:Carbodiimides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D005456:Fluorescent Dyes; D007700:Kinetics; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
D002234:Carbodiimides; D005456:Fluorescent Dyes; D000244:Adenosine Diphosphate; C038088:N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl)carbodiimide; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases