Divalent cation dependent ATPase activities of red blood cell membranes: Influence of the oxidation of membrane thiol groups close to each other

Abstract

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.

Opposing effects of oxidants and antioxidants on K+ channel activity and tone in rat vascular tissue

“…In red blood cells, diamide is known to oxidize glutathione rapidly to GSSG (Kosower, Kosower & Wertheim, 1969) which, in turn, alters the ratio of NADP: NADPH (Elkow, Moldeus & Orrenius, 1984). Oxidation of sulfhydryl groups by diamide has been shown to modulate Ca2+-Mg2+-ATPase activity (Scutari, Ballestrin & Covaz, 1980) and Ca2+ permeability (Branca, Scutari & Siliprandi, 1978). More recently, it has also been shown that the oxidation of glutathione can determine the redox status of cysteine Presented at the Oxford Meeting of the Society in July 1995. residues in the N-terminal of the fl-subunit of K+ channels and, thus, may influence channel gating (Ruppersburg, Stocker, Pongs, Heinemann, Frank & Koenen, 1991).…”