AMOEBA simulations used the AMOEBA 2013 force field for protein and ions, and the AMOEBA 2003 water model. Simulations were performed in triplicate, with unique random seeds for the thermostat and barostat. Systems were energy minimized for 2500 steps with a steepest descent algorithm, then heated to 300 K over 50 ps in the NVT ensemble, followed by equilibration to 1.0 bar over 100 ps in the NPT ensemble. Production simulations were then performed for a total of 25 ns each, with trajectory frames saved at 10 ps intervals for a total of 2500 frames per trajectory. An Andersen thermostat and Monte Carlo barostat were used to maintain temperature at 300 K and pressure at 1 bar throughout. A velocity Verlet integrator with a 1 fs timestep was used in all simulations. Long-range electrostatic interactions were treated with a Particle Mesh Ewald summation with a 7.0 Å real-space cutoff. Van der Waals interactions were subject to a 9 Å cutoff with an analytical long-range correction. Induced dipole convergence was set to 10 -5 D/atom. All MD simulations were performed with the Tinker-OpenMM plugin, using Tinker version 7.1, and OpenMM version 6.3. The WT cis-proline Amber simulation used the ff14SB force field for protein, TIP3P model for water and Joung and Cheatham parameters for ions. The system was energy minimized for 5000 steps with a steepest descent algorithm, followed by 5000 steps with a conjugate gradient algorithm. Next, the system was heated to 300 K over 50 ps in the NVT ensemble, equilibrated to 1.0 bar over 100 ps in the NPT ensemble, and simulated for a further 25 ns under NPT conditions, with trajectory frames saved every 10 ps for a total of 2500 per trajectory. A Langevin thermostat and Berendsen barostat were used to maintain temperature and pressure. A 2 fs timestep was used throughout, and the SHAKE algorithm used to constrain all bonds involving hydrogen. Long-range electrostatic interactions were treated with a Particle Mesh Ewald summation with an 8.0 Å real-space cutoff, while van der Waals interactions were calculated with an 8 Å cutoff and long-range analytical correction. MD simulations were performed with the pmemd.cuda module of the Amber14 software.