Table 1.

The distance from the oxygen atom of each threonine residue to the nearest atom of the retinal chromophore (identified with the numbering convention in Scheme S1)

Residue	Average distance, Å*	Distance, Å
		2BRD† [5]	2AT9† [7]	1QHJ‡ [9]	1C3W‡ [11]	1BRR‡ [12]	1BM1‡ [13]
Thr-17	11.74  ± 0.63	Cɛ: 11.52	Cδ: 12.90	Cδ: 11.70	Cδ: 11.56	Cγ: 11.72	Cɛ: 11.01
Thr-24	8.97  ± 1.32	Cδ: 11.52	Cγ: 9.25	Cδ: 8.28	Cδ: 8.42	Cδ: 8.31	Cδ: 8.04
Thr-46	7.25  ± 0.95	Cγ: 7.25	Cγ: 9.29	Cγ: 9.88	Cγ: 9.76	Cγ: 9.13	Cγ: 9.32
Thr-47	11.39  ± 0.42	Cγ: 10.68	Cγ: 11.65	Cγ: 11.69	Cγ: 11.66	Cγ: 11.59	Cγ: 11.04
Thr-55	10.50  ± 0.69	Cδ: 10.03	Cɛ: 10.93	Cɛ: 9.70	Cɛ: 9.94	Cδ: 11.36	Cδ: 11.02
Thr-89	3.62  ± 0.30	Cδ: 3.53	C15: 3.64	Cɛ: 3.32	Cɛ: 3.33	Cɛ: 4.12	Cδ: 3.75
Thr-90	5.09  ± 1.01	C11: 3.65	C12: 6.00	C11: 5.67	C11: 5.58	C11: 5.68	C12: 3.95
Thr-121	7.73  ± 1.43	C4: 9.28	C4: 6.50	C2: 6.52	C3: 6.30	C2: 8.66	C4: 9.12
Thr-142	4.20  ± 0.71	5-Me: 5.14	5-Me: 3.90	5-Me: 3.67	C4: 3.50	C4: 3.96	5-Me: 5.05
Thr-178	7.64  ± 0.58	13-Me: 7.64	9-Me: 7.50	13-Me: 7.35	13-Me: 7.35	13-Me: 8.79	13-Me: 7.23
Thr-205	12.72  ± 0.60	1-Me: 13.40	N: 11.79	1-Me: 12.96	1-Me: 12.67	1-Me: 13.20	1-Me: 12.28

*Average distances are shown ± SD and are taken from the six structures. 

^†Cryoelectron microscopy. 

^‡X-ray crystallography.