Figure 3
From: Structural basis for the inhibition of voltage-dependent K+ channel by gating modifier toxin
Direct interaction between VSTx1 and VSD in the DM micelles.
(a) 1H-15N HSQC spectra of uniformly 15N-labeled VSTx1 in the absence (black) and presence (red) of VSD in the DM micelles. Arrows indicate the residues disappeared upon binding to VSD. “sc” indicates side chain signals. (b) 1H-15N TROSY spectra of uniformly 2H, 15N-labeled VSD in the absence (black) and presence (red) of VSTx1 in the DM micelles. (c) Isothermal titration microcalorimetric analyses of the interaction between VSTx1 and VSD in the DM micelles. Trace of the calorimetric titration of VSTx1 into the cell containing VSD (upper panel) and the integrated binding isotherm fitted using a single-site model (lower panel) are shown. The parameters obtained from the best fit are summarized; the binding stoichiometry: 0.97 ± 0.01, the dissociation constant (Kd): 1.5 ± 0.2 μM, ΔH: −4.5 ± 0.2 kcal mol−1 and ΔS: 11.4 cal mol−1 K−1.
