Identification of the Proton Pathway in Bacterial Reaction Centers: Cooperation between Asp-M17 and Asp-L210 Facilitates Proton Transfer to the Secondary Quinone (Q_B)

The reaction center (RC) from Rhodobacter sphaeroides uses light energy to reduce and protonate a quinone molecule, QB (the secondary quinone electron acceptor), to form quinol, QBH2. Asp-L210 and Asp-M17 have been proposed to be components of the pathway for proton transfer [Axelrod, H. L., Abresch, E. C., Paddock, M. L., Okamura, M. Y., and Feher, G. (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 1542−1547]. To test the importance of these residues...