Table 1.

TDG effect on the rate of TMRM labeling of single-Cys mutants.

	LacY mutant	Helix	Fold change in TMRM labeling in RSO vesicles	Fold change in TMRM labeling in DDM
periplasmic	P31C	I	13.6	8.9
	K42C	II	8.5	5.9
	D44C	II	8.2	6.2
	Q242C	II	5.2	3.2
	N245C	VII	14.9	6.9
cytoplasmic	Q60C	II	−7.2	−3.8
	S67C	II	−14.7	−8.3
	A279C	IX	−13.1	−3.9
	L329C	X	−2.6	−3.0
	V331C	X	−5.1	−4.3

Rates of TMRM labeling were obtained from the time courses shown in Figure 3 as described (53). For each mutant, the ratio of the estimated initial rate of TMRM labeling in the presence of TDG relative to that observed in the absence of TDG was calculated. Positive numbers indicate an increase in the relative labeling rate due to addition of TDG (periplasmic cysteines) and negative numbers indicate a decrease in the relative labeling rate due to addition of TDG (cytoplasmic cysteines).