Adenylate cyclase activity in a Lubrol 12A9 extract of wild type S49 lymphoma plasma membranes is completely inactivated by incubation at 37 degrees for 20 min. Activity is restored by mixing this heated extract of wild type membranes with an unheated detergent extract of membranes from a variant clone that lacks measureable adenylate cyclase activity (AC-). The factor(s) donated by the AC- extract is labile to heating at 30 degrees (t1/2 = 3 min) or to treatment with N-ethylmaleimide or trypsin. The factor(s) donated by the heated wild type extract is also sensitive to proteases or N-ethylmaleimide. This extract displays more complex inactivation kinetics at 50 degrees, consistent with the existence of separate factors necessary for the stimulatory effects of NaF and guanyl-5'-yl-imidodiphosphate. We suggest that at least two proteins are necessary for adenylate cyclase activity and that one of these is retained in the phenotypically adenylate cyclase-deficient variant.