Table 2.

Reported Affinities of Inhibin and Activin Isoforms for Activin Receptors and Betaglycan

Receptor	Competing Ligands				Refs.
	Activin A	Activin B	Inhibin A	Inhibin B
ActRII Ki (HEK293 cells)			6.3 nm		217
ActRII Kd - displacing I125 activin A or B	49.3 ± 25 pm	3240 ± 224 pm			151
ActRII ED50 - displacing I125 activin A	0.73 ± 0.09 ng	3.26 ± 1.29 ng	15.8 ± 0.39 ng	23.7 ± 2.59 ng	151
ActRII ED50 - displacing I125 activin B	0.50 ± 0.25 ng	3.75 ± 1.02 ng	19.3 ± 6.02 ng	12.9 ± 2.62 ng	151
ActRIIB-ECD Kd - BIAcore chip analysis	0.24 nm		13.1 nm		131
ActRIIB-ECD (single) Kd -BIAcore chip analysis	6.9 nm		3.7 nm		131
ActRIIB2 (IC50) - displacing I125 inhibin A	2.2 nm		75.5 nm	20.7 nm	218
ActRIIB2 (IC50) - displacing I125 inhibin B			5.9 nm	4.5 nm	218
BG Ki (HEK293 cells)			0.6 nm		217
BG (IC50) - displacing I125 inhibin B			329 pm	533 pm	218
ActRII + BG Ki (HEK293 cells)			0.2 nm		217
ActRII + BG Kd - displacing I125 inhibin A			1100 ± 169 pm	1270 ± 37 pm	151
ActRIIB + BG Kd - displacing I125 inhibin A			433 ± 27 pm	704 ± 59 pm	151
ActRIIB2 + BG (IC50) - displacing I125 inhibin B			2.7 nm	4.0 nm	218
TM4 cells ED50 - displacing I125 inhibin A			75 pm	6000 pm	226
TM4 cells ED50 - displacing I125 inhibin B			50 pm	400 pm	226
BG (IC50) - displacing I125 inhibin A and inhibin B, respectively			4.5 nm (34 kDa)	5.0 nm (34 kDa)	78
			0.2 nm (31 kDa)	2.2 nm (31 kDa)
ActRII + BG (IC50) - displacing 31 kDa I125 inhibin A and inhibin B, respectively			1.1 nm (34 kDa)	3.5 nm (34 kDa)	78
			0.08 nm (31 kDa)	0.4 nm (31 kDa)
ActRIIB+ BG (IC50) - displacing 31 kDa I125 inhibin A and inhibin B, respectively			1.8 nm (34 kDa)	3.8 nm (34 kDa)	78
			0.3 nm (31 kDa)	0.8 nm (31 kDa)

Abbreviations: ECD, extracellular domain; BG, betaglycan.