Figure 3. Coupled interaction network at... | Rockefeller University Press

Figure 3.

Coupled interaction network at the gate. (a) Cyclic thermodynamic scheme for measuring inter-residue interaction (Δ2G0) at the gate. (b) Example MCA. Δ2G0 between L9′ in the β and δ subunits. Representative single-channel currents and dwell-time distribution histograms are shown for the background (d; Table S2), mutant A, B, and double mutant AB on the background. (c) Bar graph showing ΔΔG0 for single mutants (residues 1, 2), double mutants (residues 1 and 2 together), and Δ2G0 between these residues obtained from MCA (each residue mutated to Ala). The dotted line corresponds to 0.6 kcal mol−1, the combined error in our coupling energy measurements. Significant differences in coupling energy values (compared to βδ) are shown by asterisks (*: P < 0.05, **: P < 0.01, ***: P < 0.001). Note the stronger interaction between neighboring βδ-subunits at 9′ and 13′ positions. (d)Δ2G0 obtained between different subunit pairs (shown above) between L9′ residues in the β and δ subunits. Note the decrease in Δ2G0 in the case of aromatic residues. (e) Scatter plot showing the correlation between Δ2G0 and ΔGtrans (estimated hydrophobic effect). The straight line is a regression line passing through the scatter (slope = −1.07 ± 0.18; R2 = 0.84). There is an inverse correlation between Δ2G0 and ΔGtrans. (f) Schematic representation of the interaction strength between subunits at 9′, 12′, and 13′ positions. The pentagon represents the pentameric receptor where each of the vertices represents a subunit of AChR. Concentric pentagons (from in- to outward) represent the interacting residues at 9′, 12′, and 13′ positions, respectively. The thickness of the lines corresponds to Δ2G0 (see Table S3).

Coupled interaction network at the gate. (a) Cyclic thermodynamic scheme for measuring inter-residue interaction (Δ²G₀) at the gate. (b) Example MCA. Δ²G₀ between L9′ in the β and δ subunits. Representative single-channel currents and dwell-time distribution histograms are shown for the background (d; Table S2), mutant A, B, and double mutant AB on the background. (c) Bar graph showing ΔΔG₀ for single mutants (residues 1, 2), double mutants (residues 1 and 2 together), and Δ²G₀ between these residues obtained from MCA (each residue mutated to Ala). The dotted line corresponds to 0.6 kcal mol⁻¹, the combined error in our coupling energy measurements. Significant differences in coupling energy values (compared to βδ) are shown by asterisks (*: P < 0.05, **: P < 0.01, ***: P < 0.001). Note the stronger interaction between neighboring βδ-subunits at 9′ and 13′ positions. (d)Δ²G₀ obtained between different subunit pairs (shown above) between L9′ residues in the β and δ subunits. Note the decrease in Δ²G₀ in the case of aromatic residues. (e) Scatter plot showing the correlation between Δ²G₀ and ΔG^trans (estimated hydrophobic effect). The straight line is a regression line passing through the scatter (slope = −1.07 ± 0.18; R² = 0.84). There is an inverse correlation between Δ²G₀ and ΔG^trans. (f) Schematic representation of the interaction strength between subunits at 9′, 12′, and 13′ positions. The pentagon represents the pentameric receptor where each of the vertices represents a subunit of AChR. Concentric pentagons (from in- to outward) represent the interacting residues at 9′, 12′, and 13′ positions, respectively. The thickness of the lines corresponds to Δ²G₀ (see Table S3).