TABLE 2.
Abilities of various compounds to inhibit the uptake of choline and glycine betaine by OpuC expressed in E. coli MKH13(pMEopuC)
| Competitor | % inhibition of uptake of indicated compound with unlabeled competitor provided at indicated final concna
|
||
|---|---|---|---|
| Glycine betaine
|
Choline (1 mM) | ||
| 100 μM | 1 mM | ||
| Glycine betaine | 86 | 97 | 99 |
| Proline betaine | 65 | 94 | 99 |
| Carnitine | 38 | 82 | 98 |
| Choline | 17 | 68 | 95 |
| Acetylcholine | 7 | 36 | 87 |
| Phosphorylcholine | 9 | 12 | 66 |
| Proline | −1 | −3 | 41 |
| Ectoine | 4 | −6 | 25 |
| dl-Pipecolate | −4 | 2 | 26 |
| Trehalose | 0 | −18 | −5 |
| Glycine | −4 | 13 | −20 |
a
Cells were grown in M63 medium amended with 0.5 M of NaCl, and uptake was realized with 10 μM of [14C]glycine betaine or 10 μM of [14C]choline. The results are expressed as percents inhibition of uptake and are means for three independent experiments with variations of less than 15%. The uptake rates in the absence of competitors were 1.5 nmol/min/mg protein for choline and 19 nmol/min/mg protein for glycine betaine.