Table 1. Rates of FM quenching in... | Rockefeller University Press

Table 1.

Rates of FM quenching in different surface loops of FepA during FeEnt binding

Mutant	Loop	k (SE)	t_1/2	Rank
		s⁻¹	s
T216^a	2	1.08 (0.08)	0.64	7
T216	2	1.73 (0.04)	0.40	4
S271C^b	3	5.72 (0.81);	0.12;	1
		0.31 (0.04)	2.23
A322C	4	0.84 (0.05)	0.83	8
A383C	5	1.64 (0.15)	0.43	5
S490C	7	2.32 (0.13)	0.30	3
T550C	8	1.09 (0.06)	0.64	6
A698C	11	4.90 (0.18)	0.14	2

Mutant	Loop	k (SE)	t_1/2	Rank
		s⁻¹	s
T216^a	2	1.08 (0.08)	0.64	7
T216	2	1.73 (0.04)	0.40	4
S271C^b	3	5.72 (0.81);	0.12;	1
		0.31 (0.04)	2.23
A322C	4	0.84 (0.05)	0.83	8
A383C	5	1.64 (0.15)	0.43	5
S490C	7	2.32 (0.13)	0.30	3
T550C	8	1.09 (0.06)	0.64	6
A698C	11	4.90 (0.18)	0.14	2

We measured quenching by rapid mixing of FM-labeled FepA Cys substitution mutants (in OM fragments) with an equal volume of 200 nM FeEnt. Rates for the exponential decay processes (with parenthetic standard errors) were derived from fitting the data with GraFit 6.011; decay half times were calculated from t_1/2 = −ln 0.5/k.

Determined in live bacteria expressing FepAT216C-FM.

FepAS271C-FM was the only construct that manifested biphasic decay kinetics during FeEnt binding. The amplitudes of the first and second kinetic phases were 0.063 and 0.047, respectively. The offset was 0.28.

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