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. Author manuscript; available in PMC: 2009 Dec 2.
Published in final edited form as: J Mol Biol. 2006 Mar 9;358(4):1051–1059. doi: 10.1016/j.jmb.2006.02.050

Figure 3.

Figure 3

Functional significance of F20 and M23 residues in LacY and homologous residues F23 and W26 in CscB. (a) Time-courses of lactose accumulation by E. coli T184 expressing wild-type LacY (●), no permease (○) or LacY mutants: F20A (■), M23A (▽) and M23W (△) were measured in 50 μl aliquots of cell suspension containing 35 μg of total protein and 0.4 mM [14C]lactose as described in Materials and Methods. (b) Affinity of purified LacY mutants WT/C154G (●), F20A/C154G (■) or M23A/C154G (▽) detected by TDG protection against MIANS labeling at 0.5 μM protein and 1 μM MIANS as described in Materials and Methods. Apparent Kd values are 0.17 mM, 0.20 mM and 7 mM for WT/C154G, M23A/C154G and F20A/C154G, respectively. (c) Time-courses of sucrose accumulation by E. coli T184 expressing wild-type CscB (●), no permease (○) or CscB mutants: F23C (■), W26A (▽), W26C (△), W26F (▼) and W26M (▲) were obtained as described for Figure 2.