Divalent cation dependent ATPase activities of red blood cell membranes: influence of the oxidation of membrane thiol groups close to each other.
An Mg2+-dependent low ATPase activity can be detected in erythrocyte "white membranes," in addition to that of the well known (Ca2+ + Mg2+)-ATPase. The thiol oxidizing agent diamide affects both activities. The oxidation of neighboring thiols seems to leave the mechanism of the (Ca2+ + Mg2+)-ATPase amplification system evoked by Ca2+ largely unaffected. The perturbation caused by diamide in the membranes seems to affect primarily a step of the ATP hydrolysis mechanism that is common to both ATPase activities. The effectiveness of diamide seems to be the same when either Ca2+ and Mg2+, or Mg2+ alone are present during the reagent action. Reduction of disulfide bonds by DTE after diamide treatment restores the (Ca2+ + Mg2+)-ATPase activity but is unable to take the Mg2+-ATPase activity back to the original level. The hypothesis is discussed that the redox state of one (or more than one) couple of --SH close to each other and possibly connected to the active site, may be an important factor in optimizing the efficiency of Ca action on the (Ca2+ + Mg2+)-ATPase.
D017301:Ca(2+) Mg(2+)-ATPase; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000097:blood*; D003958:Diamide / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000032:analysis / Q000201:enzymology*; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000097:blood
D013438:Sulfhydryl Compounds; D003958:Diamide; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D008274:Magnesium; D002118:Calcium