Table 1.

cAMP receptor activity in mutant and wild-type cells

Cell type	cAMP receptor activity GTP inhibition of cAMP binding
	cAMP binding w/o GTPγS (cpm)	cAMP binding with GTPγS (cpm)	% Inhibition
AX4	5024 ± 159	1230 ± 42	75
KO	1700 ± 65	421 ± 40	75
	cAMP stimulation of GTPγS binding
	GTPγS binding w/o cAMP (cpm)	GTPγS binding with cAMP (cpm)	% of Control
AX4	6142 ± 283	9203 ± 30	150
KO	6856 ± 162	7010 ± 523	102

Specific binding was calculated by subtracting nonspecific background [cAMP binding (372 cpm) or GTPγS binding (566 cpm)] from total cpm.