2gmr

Publication Abstract from PubMed

The reaction center (RC) of Rhodobacter sphaeroides uses light energy to reduce and protonate a quinone molecule, QB (the secondary quinone electron acceptor), to form quinol, QBH2. Asp210 in the L-subunit has been shown to be a catalytic residue in this process. Mutation of Asp210 to Asn leads to a deceleration of reoxidation of QA- in the QA-QB --> QAQB- transition. Here we determined the structure of the Asp210 to Asn mutant to 2.5 A and show that there are no major structural differences as compared to the wild-type protein. We found QB in the distal position and a chain of water molecules between Asn210 and QB. Using time-resolved Fourier transform infrared (trFTIR) spectroscopy, we characterized the molecular reaction mechanism of this mutant. We found that QB- formation precedes QA- oxidation even more pronounced than in the wild-type reaction center. Continuum absorbance changes indicate deprotonation of a protonated water cluster, most likely of the water chain between Asn210 and QB. A detailed analysis of wild-type structures revealed a highly conserved water chain between Asp210 or Glu210 and QB in Rb. sphaeroides and Rhodopseudomonas viridis, respectively.

Proton uptake in the reaction center mutant L210DN from Rhodobacter sphaeroides via protonated water molecules.,Hermes S, Stachnik JM, Onidas D, Remy A, Hofmann E, Gerwert K Biochemistry. 2006 Nov 21;45(46):13741-9. PMID:17105193^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.