Is there a plasma membrane-located anion-sensitive ATPase? III. Identity of the erythrocyte enzyme with ( [formula omitted

Abstract

The characteristics of the anion-sensitive Mg 2+-ATPase activity of the rabbit erythrocyte have been studied in a lyophilized ghost preparation. The enzyme appears to be different from the anion-sensitive Mg 2+-ATPase activity of other tissues in many parameters, such as optimal pH, effects of various anions, oligomycin sensitivity and effects of Triton X-100. The enzyme is insensitive towards inhibition by irreversibly bound 4,4′-diisothiocyano-dihydrostilbene-2,2′-disulfonic acid (H 2DIDS). This excludes a relationship between the enzyme and the “band 3” protein, which is thought to be involved in the anion exchange over the erythrocyte membrane. From the effects of ethyleneglycol-bis-(β-aminoethylether)-N,N′- tetraacetic acdi (EGTA), CaCl 2, chlorpromazine and ruthenium red it is concluded that the enzyme activity does not represent a separate entity but is part of the ( Ca 2+ + Mg 2+)-ATPase system of the erythrocyte membrane. A reported stimulatory effect of carbonic anhydrase is attributed to a contamination of the carbonic anhydrase preparation by calcium and/or ( Ca 2+ + Mg 2+)-ATPase activator protein.