TABLE 4.

Various compounds inhibit proline betaine uptake in a betS mutant^a

Competitor	% Inhibition of PB uptakeb with unlabeled competitor
Glycine betaine	94
Trigonelline	9
γ-Butyrobetaine	53
Choline	70
N,N-Dimethylglycine	40
N-Methylproline	55
DMSA	84

^aCells of RmUNA369 (betS::Ω) were grown to mid-log phase in MCAA medium with 0.3 M NaCl.

^bUptake assays were performed with 40 μM PB and different competitors added at a 100-fold molar excess. The results are expressed as the percentage of inhibition of PB uptake and are means of duplicates with standard deviations of less than 5%. The control value without competitor was 2.2 nmol of PB transported per min per mg of protein.