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Fig. 3 | BMC Biology

Fig. 3

From: Structural and functional characterization of protein–lipid interactions of the Salmonella typhimurium melibiose transporter MelB

Fig. 3

Determination of in situ binding of galactosides and Na+ with RSO membrane vesicles. A FRET assay of Trp→dansyl moiety of a fluorescent sugar substrate dansyl-galactopyranoside (D2G) was used for testing the binding of galactoside and the coupling of Na+ to MelBSt in varied lipid compositions as described in the Methods. a Trace 1, collected after mixing RSO vesicles (1 mg/ml) with 10 μL D2G; trace 2, collected after consecutive addition of 20 mM NaCl; trace 3, collected upon consecutive addition of melibiose at saturating concentration. b Differential FRET (diffFRET). Left panel, diffFRET spectra upon the addition of Na+ were calculated between the trace 2 and trace 1, reflecting Na+ binding. Right panel, diffFRET spectra upon the addition of melibiose were calculated between the trace 3 and trace 2, reflecting the galactoside binding

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