TABLE 3.
Protein | Ethidium |
Na+ |
||
---|---|---|---|---|
Kta | Vmaxa | Ktb | Vmaxb | |
μm | a.u./s | mm | a.u./s | |
WT | 2.62 ± 0.17 | 0.27 ± 0.02 | 0.073 ± 0.004 | 0.10 ± 0.01 |
N174A | 2.71 ± 0.93 | 0.26 ± 0.02 | 8.8 ± 1.7c | 0.08 ± 0.03 |
F288A | 2.86 ± 0.51 | 0.21 ± 0.01 | 0.37 ± 0.10d | 0.05 ± 0.01 |
Y367A | 2.58 ± 0.03 | 0.18 ± 0.02 | 0.08 ± 0.03 | 0.05 ± 0.01 |
F395A | 24.2 ± 10.4e | 0.22 ± 0.05 | 0.10 ± 0.03 | 0.03 ± 0.01 |
D371N | 2.60 ± 0.24 | 0.04 ± 0.00 | 0.09 ± 0.03 | 0.02 ± 0.00 |
a Apparent Kt and Vmax values were determined in a facilitated ethidium efflux assay in ATP-depleted lactococcal cells at a fixed concentration of 1 mm Na+.
b Apparent Kt and Vmax values were determined in a facilitated ethidium efflux assay in ATP-depleted lactococcal cells at a fixed concentration of 2 μm ethidium.
c Significantly different substrate binding affinity compared to WT, p < 0.01.
d Significantly different substrate binding affinity compared to WT, p < 0.05.
e Significantly different substrate binding affinity compared to WT, p < 0.02.