TABLE 2.

Comparison of competition experiments between hCGβ, hLHβ, and LC Iβ chimeras

As diagrammed in Fig. 1, hLHβδ114 represents the human LHβ-subunit truncated at position 114. hLHβ-CGtail represents the human LHβ-subunit with amino acids from 114 to the C terminus replaced with those from hCG. LC Iβ-F2 is an analog containing 4 residues of hLHβ (residues 2, 8, 10, and 15) with the remaining components hCG except for residues 38–56 (where hCG residues have been replaced with those from hFSH). The α-subunit contains a cysteine in place of serine 43 in all assays. Analogs were co-transfected into COS-7 cells and quantified in A113/¹²⁵I-B110 assays. “Total dimer” represents the total amount of dimer detected. “Cross-linked dimer” represents the amount of heterodimer that remained after pH 2 treatment, 30 min at 37 °C. “% cross-linked dimer” is the ratio of cross-linked dimer to total dimer. In all analogs that contain βC26A, the β-subunit has the cysteine at position 26 replaced by alanine.

Row no.	Analogs	Total dimer	X-linked dimer	% X-linked dimer
				%
1	hLHβ	0.98 ± 0.04	0.21 ± 0.01	21
2	hCGβ	5.89 ± 0.61	0.67 ± 0.10	11
3	hLHβ C26A	0.47 ± 0.02	0.50 ± 0.02	100
4	hCGβ C26A	3.61 ± 0.17	3.41 ± 0.32	94
5	hLHβ + hLHβ C26A	0.40 ± 0.06	0.31 ± 0.04	78
6	hCGβ + hCGβ C26A	6.45 ± 0.62	1.26 ± 0.10	20
7	hLHβδ114	4.53 ± 0.18	0.43 ± 0.02	9
8	hLHβδ114 C26A	0.89 ± 0.07	0.94 ± 0.03	100
9	hLHβδ114 + hLHβδ114 C26A	0.81 ± 0.05	0.65 ± 0.05	80
10	hLHβ-CGtail	3.56 ± 0.20	0.46 ± 0.04	13
11	hLHβ-CGtail C26A	3.35 ± 0.48	3.53 ± 0.51	100
12	hLHβ-CGtail + hLHβ-CGtail C26A	3.16 ± 0.25	2.26 ± 0.30	72
13	LC Iβ-F2	0.89 ± 0.03	0.30 ± 0.01	34
14	LC Iβ-F2 C26A	1.12 ± 0.04	1.11 ± 0.02	99
15	LC Iβ-F2 + LC Iβ-F2 C26A	0.47 ± 0.02	0.37 ± 0.04	79