title: Oxygen-dependent copper toxicity: targets in the chlorophyll biosynthesis pathway identified in the copper efflux ATPase CopA deficient mutant.
abstract: Characterization of a copA(-) mutant in the purple photosynthetic bacterium Rubrivivax gelatinosus under low oxygen or anaerobic conditions, as well as in the human pathogen Neisseria gonorrhoeae identified HemN as a copper toxicity target enzyme in the porphyrin synthesis pathway. Heme synthesis is, however, unaffected by copper under high oxygen tension because of the aerobic coproporphyrinogen III oxidase HemF. Nevertheless, in the copA(-) mutant under aerobiosis, we show that the chlorophyll biosynthesis pathway is affected by excess copper resulting in a substantial decrease of the photosystem. Analyses of pigments and enzyme activity showed that under low copper concentrations, the mutant accumulated protochlorophyllide, suggesting that the protochlorophyllide reductase activity is affected by excess copper. Increase of copper concentration led to a complete lack of chlorophyll synthesis as a result of the loss of Mg-chelatase activity. Both enzymes are widely distributed from bacteria to plants; both are [4Fe-4S] proteins and oxygen sensitive; our data demonstrate their in vivo susceptibility to copper in the presence of oxygen. Additionally, our study provides the understanding of molecular mechanisms that may contribute to chlorosis in plants when exposed to metals. The role of copper efflux systems and the impact of copper on heme and chlorophyll biosynthesis in phototrophs are addressed.
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR9198, Université Paris Sud, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France.
authors.forename: Sylviane
authors.initials: S
authors.lastname: Liotenberg
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR9198, Université Paris Sud, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France.
authors.forename: Anne-Soisig
authors.initials: AS
authors.lastname: Steunou
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR9198, Université Paris Sud, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Durand
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR9198, Université Paris Sud, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France.
authors.forename: Marie-Line
authors.initials: ML
authors.lastname: Bourbon
authors.affiliation: Department of Biology, Illinois Wesleyan University, Bloomington, IL, 61702, USA.
authors.forename: David
authors.initials: D
authors.lastname: Bollivar
authors.affiliation: Copenhagen Plant Science Center, Copenhagen University, Thorvaldsensvej 40, Frederiksberg C, DK-1871, Denmark.
authors.forename: Mats
authors.initials: M
authors.lastname: Hansson
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR9198, Université Paris Sud, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France.
authors.forename: Chantal
authors.initials: C
authors.lastname: Astier
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS UMR9198, Université Paris Sud, 1 avenue de la Terrasse, 91198, Gif-sur-Yvette, France.
authors.forename: Soufian
authors.initials: S
authors.lastname: Ouchane
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics*; D000332:Aerobiosis; D001426:Bacterial Proteins / Q000378:metabolism; D020562:Betaproteobacteria / Q000235:genetics / Q000378:metabolism; D027682:Cation Transport Proteins / Q000235:genetics*; D002734:Chlorophyll / Q000096:biosynthesis* / Q000378:metabolism; D003300:Copper / Q000378:metabolism* / Q000633:toxicity; D000073840:Copper-Transporting ATPases; D003304:Coproporphyrinogen Oxidase / Q000235:genetics / Q000378:metabolism; D003305:Coproporphyrinogens / Q000378:metabolism; D006801:Humans; D008190:Lyases / Q000378:metabolism; D009344:Neisseria gonorrhoeae / Q000235:genetics / Q000378:metabolism; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D011521:Protochlorophyllide / Q000378:metabolism
chemical_list: D000251:Adenosine Triphosphatases; D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D002734:Chlorophyll; D003300:Copper; D000073840:Copper-Transporting ATPases; D003304:Coproporphyrinogen Oxidase; D003305:Coproporphyrinogens; D008190:Lyases; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010100:Oxygen; D011521:Protochlorophyllide; C028026:coproporphyrinogen III; C109194:HemN protein, Bacteria; C023886:protochlorophyllide reductase; C086788:magnesium chelatase