A protein conformational change associated with the photoreduction of the primary and secondary quinones in the bacterial reaction center.
A comparison is made between the PQA----P+QA- and PQAQB----P+QAQB-transitions in Rps. viridis and Rb. sphaeroides reaction centers (RCs) by the use of light-induced Fourier transform infrared (FTIR) difference spectroscopy. In Rb. sphaeroides RCs, we identify a signal at 1650 cm-1 which is present in the P+QA-minus-PQA spectrum and not in the P+QAQB(-)-minus-PQAQB spectrum. In contrast, this signal is present in both P+QA(-)-minus-PQA- and P+QAQB(-)-minus-PQAQB spectra of Rps. viridis RCs. These data are interpreted in terms of a conformational change of the protein backbone near QA (possible at the peptide C = O of a conserved alanine residue in the QA pocket) and of the different bonding interactions of QB with the protein in the RC of the two species.
Nabedryk
E
E
Service de Biophysique, C.E.N. Saclay, Gif-sur-Yvette, France.
Bagley
K A
KA
Thibodeau
D L
DL
Bauscher
M
M
Mäntele
W
W
Breton
J
J
D001426:Bacterial Proteins / Q000648:ultrastructure; D001429:Bacteriochlorophylls / Q000502:physiology*; D002734:Chlorophyll / Q000031:analogs & derivatives*; D010084:Oxidation-Reduction; D010674:Pheophytins / Q000502:physiology; D010788:Photosynthesis; D011487:Protein Conformation; D011809:Quinones; D012241:Rhodopseudomonas / Q000502:physiology*; D013055:Spectrophotometry, Infrared
D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D010674:Pheophytins; D011809:Quinones; D002734:Chlorophyll; C006678:bacteriopheophytin