Table 2.

Computational analysis of the interface in RI·RNase complexes

			No. of Contacts Residuesc		Character of Interface Residuesc [No. (%)]
RI·RNase Complex	Buried ASAa (Å2)	Scb	From RI	From RNase	Non-polar	Uncharged Polar	Charged	Hydrogen Bondsd (Å)	Non-bonded contactse
Humanf	2801	0.688	28	23	17 (33%)	14 (27%)	20 (39%)	19 (2.79)	177
Mouseg	2650	0.645	23	25	15 (30%)	18 (36%)	16 (33%)	13 (2.92)	126
Cowh	2793	0.605	28	25	15 (28%)	17 (32%)	21 (40%)	15 (2.90)	150
Chicken	2757	0.599	26	20	21 (46%)	7 (15%)	18 (39%)	12 (2.90)	118
Pig·Cow	2582	0.590	26	23	14 (29%)	13 (27%)	22 (45%)	8 (3.01)	90

^aBuried accessible surface area (ASA) was calculated with the program PDBsum.

^bThe value of S_c reports on geometrical shape complementarity, where S_c = 1.0 for two perfectly complementary surfaces and S_c = 0 for two completely dissimilar surfaces [74]. S_c values were calculated with SC v6.4.

^cContact residues were identified by PDBsum as non-polar (A,F,G,I,L,M,P,V,W,Y), uncharged polar (C,N,Q,S,T), or charged (D,E,H,K,R).

^dHydrogen bonds were calculated by the HBPLUS[66] algorithm of PDBsum (r_X···X<3.3 Å).

^eNon-bonded contacts were calculated by HBPLUS [66] and defined as any contacts between proteins involving either a carbon or a sulfur atom, where the interaction distance is ≤3.9 Å.

^fCalculations were performed with chain Y (hRI) and chain Z (RNase 1) from PDB entry 1z7x due to the presence of bound citrate in the active site of RNase 1 in the other complex in the asymmetric unit.

^gCalculations represent the average values from four complexes in the asymmetric unit.

^hCalculations represent the average values from two complexes in the asymmetric unit.