biostudies-literatureSugo YUniversity of TsukubaJapan Society for the Promotion of Science1544-1552https://www.ebi.ac.uk/biostudies/studies/S-EPMC10194076biostudies-literatureUnknown62(10)In photosynthetic reaction centers from purple bacteria (PbRCs), light-induced charge separation leads to the reduction of the terminal electron acceptor quinone, Q_B. The reduction of Q_B to Q_B^•- is followed by protonation via Asp-L213 and Ser-L223 in PbRC from <i>Rhodobacter sphaeroides</i>. However, Asp-L213 is replaced with nontitratable Asn-L222 and Asn-L213 in PbRCs from <i>Thermochromatium tepidum</i> and <i>Blastochloris viridis</i>, respectively. Here, we investigated the energetics of proton transfer along the asparagine-involved H-bond network using a quantum mechanical/molecular mechanical approach. The potential energy profile for the H-bond between H₃O⁺ and the carbonyl O site of Asn-L222 shows that the proton isBiochemistryMechanism of Asparagine-Mediated Proton Transfer in Photosynthetic Reaction Centers.PMC10194076JP20H05090JP20H03217JP18H01937JP18H05155Sugo YIshikita HfalseMechanism of Asparagine-Mediated Proton Transfer in Photosynthetic Reaction Centers.In photosynthetic reaction centers from purple bacteria (PbRCs), light-induced charge separation leads to the reduction of the terminal electron acceptor quinone, Q_B. The reduction of Q_B to Q_B^•- is followed by protonation via Asp-L213 and Ser-L223 in PbRC from <i>Rhodobacter sphaeroides</i>. However, Asp-L213 is replaced with nontitratable Asn-L222 and Asn-L213 in PbRCs from <i>Thermochromatium tepidum</i> and <i>Blastochloris viridis</i>, respectively. Here, we investigated the energetics of proton transfer along the asparagine-involved H-bond network using a quantum mechanical/molecular mechanical approach. The potential energy profile for the H-bond between H₃O⁺ and the carbonyl O site of Asn-L222 shows that the proton is2023-01-01T00:00:00Z2023 May2026-05-28T21:54:31.89Z2026-04-08T03:17:15.427ZS-EPMC101940763708339910.1021/acs.biochem.3c00013