TABLE 2.

Binding and transport characteristics of FeEnt uptake systems in E. coli, Salmonella, Pseudomonas, and Bordetella

Strain (growth medium supplement)	Protein	Siderophore	Binding resulta		Transport resultb
			Kd (nM)	Capacity (pmol/109 cells)	Km (nM)	Vmax (pmol/min/109 cells)	Nutrition (mm)
E. coli BN1071	EcoFepA	FeTRENCAM	27	7	370	56	15
E. coli BN1071	EcoFepA	FeEnEnt	21	20
E. coli BN1071	EcoFepA	FeEnt	17	24	394	101	18
S. typhimurium Enb7	StyFepA	FeEnt	43	38	424	101	18
P. aeruginosa K201	PaeFepA	FeEnt					NA
P. aeruginosa K201 (enterobactin)	PaeFepA	FeEnt	11	15	384	53	NA
B. bronchisepticus 19385	BbrFepA	FeEnt	1,394	6	2,300	25	NA
B. bronchisepticus 19385 (enterobactin)	BbrFepA	FeEnt	91	12	1,500	65	NA
KDF541/pITS449	EcoFepA	FeEnt	13	94	299	82	18
KDF541/pENB5	StyFepA	FeEnt	19	106	2,100c	14c	14
KDF541/pTY994	StyIroN	FeEnt	15	78	165	20	16
KD541/pCD	PaeFepA	FeEnt	18	73	312	70	20
KDF541/pKP1	BpeFepA	FeEnt	120	3

^aThe mean values for K_d and capacity were derived from three or four experiments and plotted with GRAFIT (Erithacus) using the Bound versus Total equation. The mean standard errors for the values of K_d and capacity were 24 and 9%, respectively. 

^bData from transport experiments were plotted with Grafit to yield the kinetic parameters K_m and V_max. The mean standard errors for the values of K_m and V_max were 32 and 11%, respectively. Siderophore nutrition assays were conducted twice, and little variation was observed among the trials. NA, not applicable. 

^cValues were calculated from transport experiments using an extended, 1-h uptake period. All other transport data derived from experiments with a 5-min uptake period.