title: Reconstitution and replacement of bacteriochlorophyll a molecules in photosynthetic reaction centers.
abstract: Reaction centers (RCs) of the photosynthetic bacterium Rhodobacter sphaeroides R-26 were reconstituted in liposomes after release of pigments (bacteriochlorophyll a (BChla) and bacteriopheophytin a (BPhea)) by treatment with acetone. As shown by absorption and circular dichroism spectroscopies, the reconstituted RCs had the same arrangement of pigments as the native RC and exhibited photoactivity of the special pair. The recovery yield of RCs of up to 30% was achieved by addition of 7.8-fold excess of BChla in the acetone treatment. Furthermore BChla was partially replaced with Zn-BChla by addition of the pigments during the acetone treatment. About 30% and 50% of the special pair and accessory pigments can be replaced with Zn-BChla, respectively. From this rate, an oxidation-reduction potential of 520 mV (vs. the normal hydrogen electrode NHE) was derived by the simulation of the experimental data, which is 35 mV higher than that of the native RC (484 mV vs. NHE).
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 07, Aoba-ku, Sendai 980-8579, Japan. kobayashi@biophys.che.tohoku.ac.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Atsuo
authors.initials: A
authors.lastname: Takaya
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kanai
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Ota
authors.forename: Takayuki
authors.initials: T
authors.lastname: Saito
authors.forename: Zheng-Yu
authors.initials: ZY
authors.lastname: Wang
authors.forename: Tsunenori
authors.initials: T
authors.lastname: Nozawa
mesh_terms: D000096:Acetone / Q000737:chemistry / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology; D025541:Bacteriochlorophyll A / Q000235:genetics*; D001429:Bacteriochlorophylls; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D004566:Electrodes; D006859:Hydrogen / Q000737:chemistry; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010674:Pheophytins / Q000235:genetics; D045322:Photosynthetic Reaction Center Complex Proteins / Q000502:physiology; D012242:Rhodobacter sphaeroides / Q000378:metabolism; D013053:Spectrophotometry; D013997:Time Factors; D015032:Zinc / Q000737:chemistry
chemical_list: D025541:Bacteriochlorophyll A; D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D008081:Liposomes; D010674:Pheophytins; D045322:Photosynthetic Reaction Center Complex Proteins; D000096:Acetone; C006678:bacteriopheophytin; D006859:Hydrogen; D015032:Zinc; D001205:Ascorbic Acid; D010100:Oxygen