Inactivation of angiotensin II receptors in bovine adrenal cortex by dithiothreitol: further evidence for the essential nature of disulfide bonds.

Dithiothreitol (DTT), a disulfide reducing agent, significantly decreased specific (( 3H]angiotensin II binding to membrane-bound and solubilized bovine adrenal cortical receptors. Scatchard analysis indicated a reduction in the maximum number of membrane-bound binding sites without change in affinity. The effect of DTT on membrane-bound receptors was readily reversed by the sulfhydryl oxidizing agent, 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), indicating that its action upon specific[3H]angiotensin II binding is mediated via reduction of disulfide bonds rather than other properties of this agent. Preincubation of the membranes with unlabeled angiotensin II, but not its biologically inactive precursor angiotensin I, protected the receptor from deactivation by DTT. The data provide evidence that disulfide bonds essential for[3H]angiotensin II receptor binding in bovine adrenal cortex are located at, or near, the active sites of the receptor.