Fig. S3.
Stability of WT LacY and 46W/262W mutant at pH 10.5. Sugar binding was measured as Trp151-NPG Förster resonance energy transfer (44) after preincubation of reconstituted PLs (with 14 mM protein at a lipid-to-protein ratio of 5 (wt/wt) in 50 mM CAPS pH 10.5 for given time at room temperature. (A–D) Increase of Trp fluorescence intensity (excitation at 295 nm) resulting from displacement of bound NPG (0.1 mM) by excess of TDG (6 mM) measured at pH 7.5 in 50 mM NaPi with 0.4 mM LacY. (E) Time course of LacY inactivation at pH 10.5.