Table 3.

Affinities of Bantag-1 and peptide #1 for mutants in the first extracellular domain in wild type BB₃, BB₃* and wild type BB₂ receptors (loss-of-affinity EC1 point mutations).

	Ki (nM)
	BB3*		Wild type
Receptor	Bantag-1	Peptide #1	Bantag-1	Peptide #1
BB3	5.2 ± 0.5	4.9 ± 0.8	5.6 ± 0.4	8.1 ± 1.0
BB2	ND	ND	>30,000 a	1.7 ± 0.1a
EC1 differences
[T106S]	7.4 ± 0.8	5.7 ± 0.3	6.6 ± 0.2	10.1 ± 1.0
[H107K]	283 ± 21a	6.7 ± 0.3	195 ± 51a	8.6 ± 1.9
[E111D]	5.5 ± 1.1	6.4 ± 0.9	6.2 ± 0.3	9.5 ± 1.0
[G112R]	11.6 ± 2.1b	5.3 ± 0.4	16 ± 3b	5.6 ± 1.5
Importance of H107
[H107R]	261 ± 8a	8.7 ± 2.9	>1,000	<1
[H107D]	1,000± 23 a	3.9 ± 0.9	11 ± 0.7b	2.3 ± 0.3
[H107F]	83 ± 10a	1.5 ± 0.2	24 ± 6b	4.2 ± 1.0
[H107N]	425 ± 59a	4.4 ± 0.2	318 ± 31a	4.3 ± 0.5
[H107Y]	37 ± 1a	1.9± 0.6	70 ± 3a	3.1 ± 0.4
[H107W]	>1,000 a	4.9 ± 1.9	>1,000 a	27 ± 6a

^aP <0.0001 compared with BB₃ receptor;

^bP <0.05 compared with BB₃ receptor.

ND, Not done because Arg is already present in position 288 in BB₂ receptor.

CHOP cells type were incubated with 50 pM ¹²⁵I-[D-Tyr⁶, β-Ala¹¹, Phe¹³, Nle¹⁴]Bn-(6–14) for 60 minutes at 21°C and binding was determined as described in Materials and Methods. In each experiment each value was determined in duplicate, and values given are means and S.E.M. from at least three separate experiments. Data are calculated from dose-inhibition curves shown in Fig. 1 and 4. Abbreviations: See in Fig. 1 and 2 legends.