Table 3.

Equilibrium and Kinetic Parameters for the Alkaline Transition and Imidazole Binding for Yeast Iso-1 Ferric Cyt c Variants^a

variant	kf (s−1)	kb × 102 (s−1)	Kc × 10−2	pKH	pKab	$K_{\text{app}}^{\text{Im}}$(mM−1)c	$k_{\text{off}}^{\text{Met}}$(s−1)c
WT*	41.0 ± 4.4	8.0 ± 1.5	5.1 ± 1.1	11.5 ± 0.1	8.8 ± 0.1d	0.36 ± 0.04	39 ± 13
WTe	48 ± 2	3.5 ± 1	13.9 ± 8	11.7 ± 2	8.7 ± 2	n.d.	n.d.
K79G	8.4 ± 1.9	10.6 ± 3.4	0.8 ± 0.3	10.5 ± 0.1	8.6 ± 0.1d	1.1 ± 0.1	50 ± 7
K79Ae	160 ± 5	4.0 ± 7	40 ± 70	12.0 ± 3	8.44 ± 1	n.d.	n.d.

^aThe WT and K79A variants contain tmK72 and a background C102T mutation, whereas WT* and K79G contain K72A and C102S mutations.

^bpK_a values were determined by pH titration experiments. According to the mechanism of the alkaline transition, pK_a equals the sum of pK_H and pK_c.

^c$K_{\text{app}}^{Im}$ represents the apparent binding constant of imidazole and $k_{\text{off}}^{\text{Met}}$ is the rate constant of Met80 dissociation.

^dFrom ref 28.

^eFrom ref 15.