REGULATORY COMPONENT OF ADENYLATE-CYCLASE IS LOCATED ON THE INNER SURFACE OF HUMAN-ERYTHROCYTE MEMBRANES

Human erythrocyte membranes contain the guanine nucleotide regulatory component of adenylate cyclase termed N, which can be assayed by in vitro complementation of adenylate cyclase in membranes of the cyc- variant of the S49 lymphoma cell. We used inside-out (IO) and rightside-out (RO) membrane vesicles to determine the membrane orientation of N: Trypsin inactivates N in IO but not in RO vesicles. Treatment with cholera toxin and NAD+ activates N in IO but not in RO vesicles. These experiments provide strong evidence that N is located on the inner surface of the human erythrocyte membrane. © 1979.