Fig. 2. Substrate binding by single-W151C154G LacY. Time courses of MIANS labeling of purified detergent-solubilized LacY in the absence or presence of
different sugars are shown. Reactions were initiated by adding 5 MMIANS to 1 MLacY. Fluorescence was recorded as described in Experimental Procedures.
(A) Protection against MIANS labeling of single-W151C154G LacY by given concentrations of TDG. (B) Effect of TDG, melibiose, or glucose (15 mM final
concentration) on the rate of MIANS labeling.