Table 1.

Responses to IP₃ analogues. The effects of each analogue on Ca²⁺ release from the intracellular stores of permeabilized DT40-IP₃R1 cells and on ³H-IP₃ binding to full-length purified IP₃R1 (FL), its N-terminal (NT, residues 1-604) or the IP₃-binding core (IBC, residues 224-604) are summarized (n ≥ 4). For dimers, the estimated separation of the two moieties is shown calculated as in⁵⁰. Results are means ± SEM. *No detectable Ca²⁺ release with 30μM 8. ND, not determined.

		Ca2+ release		FL		NT	IBC
		EC50 (nM)	Release %	Kd (nM)	EC50/Kd	Kd (nM)	Kd (nM)
1	IP3	20±2	77±5	12.5±1.06	1.6±0.2	2.82±0.26	0.21±0.03
13	AdA	1.5±0.1	75±6	1.26±0.11	1.2±0.01	ND	ND
2	(IP3)2 0.8nm	2.7±0.4	76±6	0.45±0.04	6.0±1.0	0.41±0.03	0.18±0.01
3	(IP3)2 1.5nm	4.9±0.3	74±6	0.86±0.19	5.7±1.3	0.47±0.09	0.18±0.01
4	(IP3)2 8nm	13±1	73±7	1.39±0.23	9.3±1.6	1.37±0.20	0.48±0.02
5	IP3–L-IP3 0.8nm	5±1	70±7	0.90±0.12	5.6±1.3	0.42±0.02	0.14±0.02
6	IP3–IP5 0.8nm	5±0	72± 5	0.89±0.11	5.6±0.7	0.36±0.03	0.20±0.01
7	IP3–Ins 0.8nm	21±1	76±4	7.82±1.73	2.7±0.6	2.81±0.22	0.33±0.01
8	(L-IP3)2 0.8nm	Inactive*	ND	ND	ND	ND	ND
9	2-adamantane-IP3	30±3	71±1	7.62±0.51	3.9±0.5	1.63±.022	0.20±0.02
10	2-deoxy-IP3	32±7	65±3	17.1±1.1	1.9±0.4	4.01±0.38	0.22±0.03
11	2-aminoethyl-IP3	42±5	69±6	43.6±4.6	0.95±0.02	13.5±2.0	0.52±0.04