Table 2. Dissociation Constants for the BfrB:Bfd Interaction Involving Mutant BfrB and Bfd Molecules and Corresponding Initial Rates of Iron Release from the Core of BfrB.

protein	Kd (μM) (pH 7.4)	initial rate (min–1)
wild type	3.3 ± 0.5	0.099 ± 0.007
BfrB E81A	258.5 ± 21.5	0.031 ± 0.0003
BfrB L68A	298.5 ± 20.5	0.019 ± 0.0003
BfrB E85A	590 ± 2	0.018 ± 0.0006
BfrB L68A/E81A	not measurable	not measurable
Bfd Y2F	10.7 ± 0.2	0.097 ± 0.004
Bfd K40A	7.7 ± 0.5	0.090 ± 0.002
Bfd L5A	82 ± 2.5	0.044 ± 0.0005