Table 3.

Apparent dissociation constants (K_d) for the dialyzable zinc in σ^E/ChrR complexes containing wild type or variant ChrR proteins¹

ChrR Protein	Kd (M)	Relative Affinity
WT	4.6 × 10−10	1.00
H141A	9.7 × 10−10	0.48
H143A	5.6 × 10−9	0.08
E147A	1.6 × 10−8	0.03
H177A	5.1 × 10−9	0.09
C187A	3.9 × 10−10	1.16
C189A	3.9 × 10−10	1.16
C187S	5.1 × 10−9	0.09
C189S	1.1 × 10−9	0.04

¹Apparent K_d values were calculated based on the dissociation constant of Zinbo-5 (K_d = 1.3 × 10⁻⁹ M), as described in materials and methods. Values in “Relative Affinity” column were calculated by dividing K_d value of σ^E/ChrR complexes containing wild type ChrR to those measured for those containing the indicated variant ChrR protein. Experiments were conducted in three separate trials with separate protein preparations. Results shown are representative data from one experimental trial. In each trial, similar trends in relative affinity for zinc were observed between samples.