Inhibition of anion permeability of sarcoplasmic reticulum vesicles by stilbene derivatives and the identification of an inhibitor-binding protein

The permeability of sarcoplasmic reticulum vesicles to sulfate ions was inhibited by diisothiocyano-1,2-diphenylethane-2,2′-disulfonic acid (H₂DIDS), which is a potent inhibitor of anion permeability in red blood cell membrane. The amount of H₂DIDS bound to the vesicles was determined by using ³H]-H₂DIDS. Apparent half inhibition of sulfate permeation was observed on the binding of 2.5 μmol/g protein. SDS-polyacrylamide gel electrophoresis of the vesicles treated with ³H]H₂DIDS showed that about 10% of the total bound H₂DIDS corresponds to a 100 000-dalton protein, but the remaining 90% to non-protein components. The content of the H₂DIDS-binding protein was about 0.5 μmol/g protein. These results suggest that the H₂DIDS-binding protein is different from the calcium pump protein and is possibly an anion transport system similar to band 3 in red blood cell membrane.