title: Rhodobacter sphaeroides mutants overexpressing chlorophyllide a oxidoreductase of Blastochloris viridis elucidate functions of enzymes in late bacteriochlorophyll biosynthetic pathways.
abstract: In previous studies we have demonstrated that chlorophyllide a oxidoreductases (CORs) from bacteriochlorophyll (BChl) a-producing Rhodobacter species and BChl b-producing Blastochloris viridis show distinct substrate recognition and different catalytic hydrogenation reactions, and that these two types of CORs therefore cause committed steps for BChls a and b biosynthesis. In this study, COR genes from B. viridis were incorporated and overexpressed in a series of Rhodobacter sphaeroides mutants. We found that the following two factors are essential in making R. sphaeroides produce BChl b: the loss of functions of both intrinsic COR and 8-vinyl reductase (BciA) in the host R. sphaeroides strain; and expression of the BchYZ catalytic components of COR from B. viridis, not the complete set of COR (BchXYZ), in the host strain. In addition, we incorporated bchYZ of B. viridis into the R. sphaeroides mutant lacking BchJ and BciA, resulting in the strain accumulating both BChl a and BChl b. This is the first example of an anoxygenic photosynthetic bacterium producing BChls a and b together. The results suggest that BchJ enhances activity of the intrinsic COR. The physiological significance of BchJ in pigment biosynthetic pathways will be discussed.
authors.affiliation: 1] Graduate School of Life Sciences, Ritsumeikan University, Shiga 525-8577, Japan [2] PRESTO, Japan Science and Technology Agency, Saitama 332-0012, Japan [3] Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Tsukatani
authors.affiliation: Department of Medical Biochemistry, Kurume University School of Medicine, Fukuoka 830-0011, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Harada
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
authors.forename: Jiro
authors.initials: J
authors.lastname: Nomata
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
authors.forename: Haruki
authors.initials: H
authors.lastname: Yamamoto
authors.affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Fujita
authors.affiliation: Graduate School of Life Sciences, Ritsumeikan University, Shiga 525-8577, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mizoguchi
authors.affiliation: Graduate School of Life Sciences, Ritsumeikan University, Shiga 525-8577, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tamiaki
mesh_terms: D001429:Bacteriochlorophylls / Q000096:biosynthesis*; D053898:Biosynthetic Pathways; D002851:Chromatography, High Pressure Liquid; D004789:Enzyme Activation; D015870:Gene Expression; D009154:Mutation; D010105:Oxygenases / Q000235:genetics* / Q000378:metabolism; D010860:Pigments, Biological / Q000737:chemistry / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001429:Bacteriochlorophylls; D010860:Pigments, Biological; D010105:Oxygenases; C115272:chlorophyll a oxygenase