TABLE 4.

Kinetic analysis of sodium-coupled downhill melibiose transport^a

Strain	Mean apparent Km (mM) ± SE	Mean apparent Vmax (nmol of melibiose/min/mg of protein) ± SE
Wild-type	0.22 ± 0.06	71 ± 14
R52K	0.24 ± 0.05	153 ± 55
R52S	0.75 ± 0.06	18 ± 3
R52S W116R	0.63 ± 0.02	64 ± 10
R52S S247R	2.7 ± 0.3	50 ± 3
R52S N248K	0.24 ± 0.06	39 ± 8
R52S D55N	7.4 ± 1.7	209 ± 57
R52S P60Q	6.5 ± 1.0	40 ± 3
R52S N244S	2.4 ± 0.48	72 ± 14
R52S I352V	1.2 ± 0.08	48 ± 10

^aTransport of melibiose after 30 s was measured at six different concentrations which bracketed an initial estimate of the K_m for each strain. The values for K_m and V_max are the averages of at least two separate experiments with three datum points in each experiment. Transport was done in the presence of 10 mM Na⁺ for all strains except for the R52S D55N strain for which 100 mM Na⁺ was required.