Fig. 2. (A) Fluorescence spectra of YFP-MetQ mutants containing CouA at the indicated position in the presence and absence of l-Met. Assay conditions: 100 nM sensor protein, 50 mM phosphate buffer (pH 9.0), 50 mM NaCl, and 10 μM l-Met. (B) Changes in FRET ratio of YFP-MetQ mutants calculated from data in Fig. 2A. FRET ratios were calculated from ICouA, 468 nm and IYFP, 537 nm upon excitation at 360 nm in the presence and the absence of l-Met. FRET ratio changes were calculated from eqn (1). Each data point represents an average of three independent experiments.
