Skip to main content
. Author manuscript; available in PMC: 2019 Apr 23.
Published in final edited form as: Biochemistry. 2016 Oct 12;55(42):5917–5926. doi: 10.1021/acs.biochem.6b00826

Fig. 6. Thermodynamic cycle of Nbs and galactoside binding to WT or double-Trp LacY.

Fig. 6.

(a) WT LacY. (b) Double-Trp mutant. State A in (a), cartoon of simulated model of WT LacY based on the crystal structure (2V8N) represents an inward-facing, lowest free energy state3. State A in b, cartoon of simulated double-Trp mutant model of outward-facing state13, 56. States B in a and b, proposed Nb-9036-bound outward-facing conformation15. State C in a and b, cartoons based on crystal structures of double-Trp mutant with occluded galactoside (4OAA, or 4ZYR)7, 8. State D in a and b, occluded intermediate where koff of galactoside is markedly inhibited15. Histograms are from Tables 1 and 2, and ΔG, ΔH -TΔS are labeled with a scale at the right side. (c) Thermodynamic cycle analysis. Conformational change from A to B to D is expressed as the A-B-D path, and from A to C to D is expressed as the A-C-D path. The free energy difference between the two paths is expressed by ΔΔG[ABD]-[ACD]. The data for both Nb-9036 and 9065 are from tables 1 and 2.