Table 3. The correlation between the evolutionary variability of the site (s) and the number of specific protein–DNA interactions: hydrogen bonds and hydrophobic interactions.

Factor	N	NHB	NHF	Correlation coefficient
				n	nHB	nHF
Crp	150	6	14	–0.77	–0.50	–0.50
PurR	220	14	30	–0.61	–0.35	–0.60
Ihf	206	4	11	–0.74	–0.10	–0.76
TrpR	215	3	17	–0.47	–0.07	–0.35
TrpR SELEX	215	3	17	–0.61	–0.24	–0.47
MetJ	128	9	11	–0.34	–0.28	0.03
MetJSELEX holo	128	9	11	–0.67	–0.67	–0.43
MetJ SELEX apo	128	9	11	–0.62	–0.66	–0.43

R_cutoff = 4.5 Å. N = Σ_i n_i is the total number of all interactions between the base pairs and the protein, including N^HB = Σ_i hydrogen bonds and N^HF = Σ _i hydrophobic interactions. Statistically significant values (P < 2.5%) are shown in bold.