title: Influence of the H-subunit and Fe2+ on electron transport from I- to QA in Fe(2+)-free and/or H-free reaction centers from Rhodobacter sphaeroides R-26.
abstract: From reaction centres (RC) of Rhodobacter sphaeroides R-26 two LM preparations with 0.90 Fe2+/RC (LM) and 0.10 Fe2+/RC (LM/dFe) were prepared. Reconstitution of LM/dFe with the H-subunit and subsequently with Zn2+ yielded LMH/dFe and LMH/dFe and LMH/dFe + Zn preparations, respectively. In these four samples the decay of the primary radical pair P+I- was studied by means of transient absorption spectroscopy and compared with that in native RC. In LMH/dFe the reduction of QA by Bpheo a occurred in 5 ns, with concomitant increase in the yield of PT, the triplet state of the primary donor. In the LM/dFe, LM and LMH/dFe + Zn preparations the decay of I- had the same rate (200 ps)-1 as in native RC. Thus, neither the H-subunit in the RC nor a divalent metal as Fe2+ or Zn2+ are necessary per se for fast reduction of QA. Only demetallation in the presence of the H-subunit slows down the reduction of QA.
authors.affiliation: Department of Biophysics, Huygens Laboratory, Leiden University, The Netherlands.
authors.forename: B L
authors.initials: BL
authors.lastname: Liu
authors.forename: P J
authors.initials: PJ
authors.lastname: van Kan
authors.forename: A J
authors.initials: AJ
authors.lastname: Hoff
mesh_terms: D002413:Cations, Divalent; D004579:Electron Transport; D006859:Hydrogen / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D007700:Kinetics; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D011809:Quinones / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D045322:Photosynthetic Reaction Center Complex Proteins; D011809:Quinones; D006859:Hydrogen; D007501:Iron