Table 3.

Hydrogen bonds of the 270-loop

Amino acid	Hydrogen bond(s), distance(s)a at position:
	267	268	269	270	272	273	274	275	276
18N1 (3BEQ)	Arg219, 3.47; Ser251, 2.67	Tyr252, 2.83; Ala270, 3.15	Tyr312, 2.94	Gln249, 3.12; Tyr273, 3.08	Gln249, 2.84; His296, 2.77	Gln249, 3.47; Tyr252, 2.64	Pro245, 3.04; Asn294, 3.00; Tyr316, 3.28	Thr242, 2.69; Trp302, 2.70	Arg224, 2.88, 3.21; Arg292, 2.91, 2.95
VN04N1 (2HTY)	Ser251,2.46	Tyr252, 2.82; Ala270, 3.12	Tyr312, 2.85	Gln249, 3.24; Tyr273, 2.91	Gln249, 2.43, 3.33; His296, 3.22, 3.41	Tyr252, 2.67; Gln249, 3.34	Pro245, 3.15; Asn294, 3.17; Tyr316, 3.46	Thr242, 2.63; Trp302, 2.77	Arg224, 2.77, 2.80; Arg292, 2.80, 2.93
09N1 (3NSS)	Ser251, 2.69	Ala270, 3.14	Tyr312, 2.76	Gln249, 3.27; Tyr273, 3.19	Gln249, 2.74; His296, 2.83	Tyr252, 2.63; Ala270, 3.19	Pro245, 3.10; Asn294, 3.03; Tyr316, 3.38	Thr242, 2.68; Trp302, 2.74	Arg224, 2.77, 3.22; Arg292, 2.84, 2.84
N4 (2HTV)		Tyr252, 2.86; Ala270, 3.35	Tyr312, 3.11	Gly272, 3.20; Phe272, 2.78	Gln249, 2.48; Arg296, 3.15, 3.43	Gln249, 3.44; Tyr252, 2.69; Ala270, 2.78	Pro245, 3.07; Asn294, 3.03; Tyr316, 3.49	Tyr252, 3.48; Thr242, 2.74	Arg224, 3.09, 3.17; Arg292, 2.93, 3.06
N5 (3SAL)	Ser251, 2.72	Tyr252, 2.79; Phe270, 3.44	Tyr312, 2.77	Gln249, 3.21; Gly273, 2.96	Gln249, 2.81	Gln249, 3.44; Phe270, 2.96	Pro245, 3.18; Asn294, 3.06; Tyr316, 3.50	Thr242, 2.70	Arg224, 2.68, 2.98; Arg292, 2.81, 2.88
N8 (2HT5)	Arg252, 2.78, 3.43; Tyr312, 3.37	Tyr252, 2.81	Tyr312, 2.91	Gln249, 2.83; Gly273, 2.86		Gln249, 2.62; Tyr252, 2.51; Phe270, 2.86	Pro245, 3.19; Gly294, 3.02	Thr242, 2.63	Arg224, 2.74, 2.75; Arg292, 2.85, 2.88
N2 (1NN2)		Thr252, 3.20	Ser314, 2.82		Ser314, 2.79	Lys296, 2.87; Tyr316, 3.05	Ala246, 2.53; Gly248, 2.89		Arg224, 2.94; Arg292, 2.83, 2.96
N3 (4HZV)	Tyr251, 2.76		Ser248, 2.92; Ala249, 2.61; Gln273, 2.92		Gln273, 3.42	Tyr252, 2.72; Lys269, 2.92; Ile272, 3.42; Lys295, 2.93; Tyr316, 3.04	Tyr252, 3.06; Glu276, 3.39	Thr241, 2.96	Arg224, 2.59, 2.93; His274, 3.39; Arg292, 2.78, 2.90
N6 (1V0Z)		Thr252, 2.88	Ser314, 2.71		Ser314, 2.97	Arg249, 3.05; Tyr316, 3.04	Glu276, 2.95	Thr242, 2.71	Arg224, 2.80, 2.86; His274, 2.95; Arg292, 2.74, 2.92
N9 (7NN9)		Thr252, 2.96	Ser314, 2.62		Ser314, 3.08	Tyr316, 2.86	Ser245, 3.01; Asn294, 3.37	Thr242, 2.67	Arg224, 2.75, 3.21; Arg292, 2.86, 2.89

^aAll hydrogen bond distances refer to molecule A of each structure.