Table 1. Mutations created and analyzed.

Residue	Structure	mutations	φ ± SE	Range energy (kcal/mol)
K46	PP	Q, M, R	0.29 ± 0.58	0.43
Y55	D loop	F, Q, S	0.56 ± 0.38	0.24
L93	A loop	A, T, Y	0.52 ± 0.32	0.47
N96	Col	S, V*, W	0.07 ± 0.24	0.52
V132		A, Q, L	-0.12 ± 0.10	0.77
Y149	B loop & Col	A, D, Q, S	0.73 ± 0.26	0.48
N182		D, E, S	0.15 ± 0.29	0.18
G183		F, W, Y	0.69 ± 0.15	0.55
Q184		T, W	-0.37 ± 0.46	0.40
I218	Pre-M1	T, V	0.69 ± 0.66	0.25
R219	Pre-M1	I, K, Q	0.27 ± 0.07	0.76
R220	Pre-M1 & PP	I*, Q, K	6.88 ± 7.88	0.02
K221	Pre-M1	I, Q, R	0.52 ± 0.28	0.54
S257	TM2	C, G, I	-0.05 ± 0.32	0.67
A260	TM2	C, G, V	0.03 ± 0.25	0.80
T265	TM2	P, S, Y	0.42 ± 0.31	0.93
V266	TM2 & Col	A, F, T	0.48 ± 0.07	2.01
L270	TM2	A, T, Y	0.53 ± 0.18	2.80
V275	TM2-link-TM3	A, L, M	0.24 ± 0.27	1.19
P276	TM2-link-TM3 & Col	G, K, T	0.24 ± 0.27	1.26
L280	TM2-link-TM3 & PP	A, T, Y	-0.30 ± 0.27	0.50
A281	TM2-link-TM3	F, T, W	0.34 ± 0.24	0.45
V282	TM2-link-TM3	A, Q, L	0.31 ± 0.08	0.67
P283	TM2-link-TM3 & PP & Col	A, G, S	0.16 ± 0.28	0.62
I284	TM2-link-TM3	F, L, T	0.52 ± 0.12	0.78
I285	TM2-link-TM3	F, L, T	0.24 ± 0.15	1.44
I286	TM2-link-TM3	F, L, T	0.48 ± 0.04	1.03

The first column shows the residue studied. The second shows structural features, where PP indicates a residue in the Principal Pathway and "Col" a residue in the high energy column (see Text). The 3rd column shows the mutations made (an asterisk indicates that no functional channels were recorded from receptors containing that mutated subunit). The 4th column gives φ ± the estimated SE returned by the fitting program. The final column gives range energy (kcal/mol). Positions at which the range energy is greater than 0.7 kcal/mol are shown in bold.