Coupling of light-induced electron transfer to proton uptake in photosynthesis.
Light energy is transformed into chemical energy in photosynthesis by coupling a light-induced electron transfer to proton uptake. The resulting proton gradient drives ATP synthesis. In this study, we monitored the light-induced reactions in a 100-kDa photosynthetic protein from 30 ns to 35 s by FTIR difference spectroscopy. The results provide detailed mechanistic insights into the electron and proton transfer reactions of the QA to QB transition: reduction of QA in picoseconds induces protonation of histidines, probably of His126 and His128 in the H subunit at the entrance of the proton uptake channel, and of Asp210 in the L subunit inside the channel at 12 micros and 150 micros. This seems to be a prerequisite for the reduction of QB, mainly at 150 micros. QA- is reoxidized at 1.1 ms, and a proton is transferred from Asp210 to Glu212 in the L subunit, the proton donor to QB-. Notably, our data indicate that QB is not reduced directly by QA- but presumably through an intermediary electron donor.
Remy
André
A
Lehrstuhl für Biophysik, Ruhr-Universität Bochum, Postfach 102148, 44780 Bochum, Germany.
Gerwert
Klaus
K
D004579:Electron Transport / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D046911:Macromolecular Substances; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000502:physiology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D018892:Proton-Motive Force / Q000528:radiation effects; D011809:Quinones / Q000737:chemistry; D012242:Rhodobacter sphaeroides / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D017550:Spectroscopy, Fourier Transform Infrared
D046911:Macromolecular Substances; D045322:Photosynthetic Reaction Center Complex Proteins; D011809:Quinones