title: Time-resolved crystallographic studies of light-induced structural changes in the photosynthetic reaction center.
abstract: Light-induced structural changes in the bacterial reaction center were studied by a time-resolved crystallographic experiment. Crystals of protein from Blastochloris viridis (formerly Rhodopseudomonas viridis) were reconstituted with ubiquinone and analyzed by monochromatic and Laue diffraction, in the dark and 3 ms after illuminating the crystal with a pulsed laser (630 nm, 3 mJ/pulse, 7 ns duration). Refinement of monochromatic data shows that ubiquinone binds only in the "proximal" Q(B) binding site. No significant structural difference was observed between the light and dark datasets; in particular, no quinone motion was detected. This result may be reconciled with previous studies by postulating equilibration of the "distal" and "proximal" binding sites upon extended dark adaption, and in which movement of ubiquinone is not the conformational gate for the first electron transfer between Q(A) and Q(B).
authors.affiliation: Department of Chemistry, University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA.
authors.forename: Richard H G
authors.initials: RH
authors.lastname: Baxter
authors.forename: Nina
authors.initials: N
authors.lastname: Ponomarenko
authors.forename: Vukica
authors.initials: V
authors.lastname: Srajer
authors.forename: Reinhard
authors.initials: R
authors.lastname: Pahl
authors.forename: Keith
authors.initials: K
authors.lastname: Moffat
authors.forename: James R
authors.initials: JR
authors.lastname: Norris
mesh_terms: D018360:Crystallography, X-Ray; D005583:Fourier Analysis; D008027:Light; D008958:Models, Molecular; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000528:radiation effects*; D011487:Protein Conformation; D012241:Rhodopseudomonas / Q000737:chemistry / Q000528:radiation effects
chemical_list: D045322:Photosynthetic Reaction Center Complex Proteins