Role of water and protein electrostatic interactions in the stability of the protonated retinal Schiff base of resting state C1C2.

<p>(a) PMF profiles computed for direct proton transfer to D292 in wild-type C1C2 with unprotonated E162. We compare the PMF profiles computed for C1C2 in a hydrated lipid membrane environment (full, black line, Path 1 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0201298#pone.0201298.t005" target="_blank">Table 5</a>), for C1C2 with lipids and bulk water removed (PROT, grey line, Path 9) and for C1C2 with all active site waters removed (DRIER, dashed line, Path 13). (b) Testing the impact of the K132A mutation on proton transfer. We show PMF profiles computed for direct proton transfer to D292, when E162 is protonated. We compare PMF profiles computed for wild-type C1C2 in the full (solid black line, Path 4), the PROT (solid grey, Path 10) and the DRIER setups (black dashes, Path 14) to PMF profiles computed for the K132A mutant in the full (solid magenta, Path 18) and the DRIER setup (magenta dashes, Path 21). We note that, for direct proton transfer in K132A with unprotonated E162, pathway calculations did not converge and were not used in the analysis.