Fig. 5.

Examples of hydrogen bonding (black dashed lines) during simulation and how they change with the protonation of E14. Monomers A and B are drawn in blue and red, respectively. (A) Example interaction network surrounding deprotonated E14, highlighting multiple influential interactions to ${\mathrm{E}\mathrm{14}}^{\text{A}}$. These include ${\mathrm{W}\mathrm{63}}^{\text{A}}$, ${\mathrm{Y}\mathrm{60}}^{\text{B}}$, and an example of water-mediated interaction (${\mathrm{S}\mathrm{43}}^{\text{A}}$). Helices 1 and 2 of monomer B have been omitted for clarity, as have hydrogen atoms not directly involved in hydrogen bonds. (B) Example interaction network when ${\mathrm{E}\mathrm{14}}^{\text{B}}$ is protonated, detailing how E14 can act as a donor to the backbone of ${\mathrm{W}\mathrm{63}}^{\text{B}}$ rather than as an acceptor as it was in A, which in turn changes ${\mathrm{W}\mathrm{63}}^{\text{B}}$ into a potential donor for ${\mathrm{S}\mathrm{43}}^{\text{B}}$.