TABLE 3.
Downhill melibiose transport
| melB strain | Amt of melibiose transporteda in the presence of:
|
|||
|---|---|---|---|---|
| H+ | 10 mM Na+ | 100 mM Na+ | 10 mM Li+ | |
| Wild-type | 35 ± 9 | 149 ± 40 | 42 ± 2 | 87 ± 4 |
| R52K | 50 ± 5 | 206 ± 17 | 98 ± 5 | 148 ± 11 |
| R52Q | 4 ± 1 | 8 ± 1 | 4 ± 1 | 2 ± 1 |
| R52V | 0 ± 0 | 0.1 ± 0.1 | 4 ± 1 | 0.9 ± 0.3 |
| R52S | 0.2 ± 0.1 | 12 ± 4 | 8 ± 1 | 4 ± 0.3 |
| R52S W116R | 6 ± 0.7 | 99 ± 7 | 93 ± 9 | 68 ± 7 |
| R52S S247R | 2 ± 2 | 25 ± 11 | 13 ± 1 | 22 ± 2 |
| R52S N248K | 2 ± 0.5 | 60 ± 19 | 31 ± 1 | 81 ± 16 |
| R52V T338R | 1 ± 1 | 3 ± 0.4 | 10 ± 1 | 6 ± 1 |
| R52S D19G | 0.8 ± 0.4 | 2 ± 1 | 8 ± 1 | 4 ± 0.7 |
| R52S D55N | 2 ± 0.4 | 23 ± 1 | 65 ± 2 | 9 ± 0.7 |
| R52S P60Q | 0.9 ± 0.1 | 15 ± 7 | 6 ± 2 | 7 ± 0.6 |
| R52S N244S | 1 ± 0.3 | 41 ± 3 | 19 ± 7 | 18 ± 0.9 |
| R52S I352V | 4 ± 3 | 40 ± 16 | 33 ± 1 | 20 ± 0.9 |
a
The concentration of radiolabeled melibiose was 0.8 mM, and values given represent transport at 10 min. The values are given in nanomoles of [3H]melibiose per milligram of protein. Transport values were calculated, assuming 0.1 mg of protein for every 6 × 108 cells. The data are averages of at least two separate experiments with duplicate determinations in each experiment ± standard errors.