Table 1

Affinities of CCK-9 and modified peptides for the WT-CCK2R, Y189F (Y4.60F) mutant, and N358A (N6.55A) mutant

	WT- CCK2R		Y189F Mutant		N358A Mutant
	K_i	F_CCK-9	K_i	F_CCK-9	K_i	F_CCK-9
	nM		nM		nM
CCK-9	1.3 ± 0.3	1	39.3 ± 5.6	1	24.2 ± 5.3	1
(PheCH₃)⁹-CCK	17.4 ± 3.2	13	252 ± 42	6	26.1 ± 7.8	1
(Phenylethylamide)⁹-CCK	341 ± 53	262	816 ± 157	21	543 ± 154	22
(Ala)³-CCK	18.1 ± 6.1	14	382 ± 15	10	233 ± 55	10

K_i values were calculated from competition curves of ¹²⁵I-BH-CCK-9 binding by the indicated ligand as described under Materials and Methods. The factor F_CCK-9 represents the effect of the mutation on the affinity of the ligand tested relative to CCK-9. Results are expressed as mean ± S.E. of three to five separate experiments performed in duplicate.