ASYMMETRICAL DISTRIBUTION OF THIOL-GROUPS INVOLVED IN ATP-PI-32 EXCHANGE ON MITOCHONDRIAL-MEMBRANES

The use of mitoplasts, that is mitochondria devoid of outer membrane oriented as normal mitochondria, and of sonicated vesicles, the membrane of which is inside-out has shown that the thiol groups involved in the process of ATP synthesis are on the matrix face of the mitochondrial membrane: carboxypyridine disulfide (CPDS) a thiol reagent that cannot penetrate across hydrophobic membranes does not inhibit the ATP-32Pi exchange catalyzed by mitoplasts, while 5,5′-dithio-bis-(2-nitrobenzoate), which penetrates more readily, can completely inhibit this exchange. In contrast, both reagents react similarly with inside-out vesicles. The nature of the component of the ATPase-ATP synthase complex to which this thiol group may belong is discussed. © 1978.