title: [NiFe]-hydrogenase is essential for cyanobacterium Synechocystis sp. PCC 6803 aerobic growth in the dark.
abstract: The cyanobacterium Synechocystis sp. PCC 6803 has a bidirectional [NiFe]-hydrogenase (Hox hydrogenase) which reversibly reduces protons to H2. This enzyme is composed of a hydrogenase domain and a diaphorase moiety, which is distinctly homologous to the NADH input module of mitochondrial respiratory Complex I. Hox hydrogenase physiological function is still unclear, since it is not required for Synechocystis fitness under standard growth conditions. We analyzed the phenotype under prolonged darkness of three Synechocystis knock-out strains, lacking either Hox hydrogenase (ΔHoxE-H) or one of the proteins responsible for the assembly of its NiFe active site (ΔHypA1 and ΔHypB1). We found that Hox hydrogenase is required for Synechocystis growth under this condition, regardless of the functional status of its catalytic site, suggesting an additional role beside hydrogen metabolism. Moreover, quantitative proteomic analyses revealed that the expression levels of several subunits of the respiratory NADPH/plastoquinone oxidoreductase (NDH-1) are reduced when Synechocystis is grown in the dark. Our findings suggest that the Hox hydrogenase could contribute to electron transport regulation when both photosynthetic and respiratory pathways are down-regulated, and provide a possible explanation for the close evolutionary relationship between mitochondrial respiratory Complex I and cyanobacterial [NiFe]-hydrogenases.
authors.affiliation: Department of Biology University of Padova, Viale G. Colombo 3, 35131 Padova, Italy.
authors.forename: Edith
authors.initials: E
authors.lastname: De Rosa
authors.affiliation: 1] Department of Biology University of Padova, Viale G. Colombo 3, 35131 Padova, Italy [2] Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Checchetto
authors.affiliation: 1] Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy [2] Proteomics Center of Padova University, Via G. Orus 2/B, 35129 Padova, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Franchin
authors.affiliation: Department of Biology University of Padova, Viale G. Colombo 3, 35131 Padova, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Bergantino
authors.affiliation: Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Berto
authors.affiliation: Department of Biology University of Padova, Viale G. Colombo 3, 35131 Padova, Italy.
authors.forename: Ildikò
authors.initials: I
authors.lastname: Szabò
authors.affiliation: Department of Biology University of Padova, Viale G. Colombo 3, 35131 Padova, Italy.
authors.forename: Giorgio M
authors.initials: GM
authors.lastname: Giacometti
authors.affiliation: 1] Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy [2] Proteomics Center of Padova University, Via G. Orus 2/B, 35129 Padova, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Arrigoni
authors.affiliation: Department of Biology University of Padova, Viale G. Colombo 3, 35131 Padova, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Costantini
mesh_terms: D000332:Aerobiosis; D003623:Dark Adaptation; D006864:Hydrogenase / Q000378:metabolism*; D046939:Synechocystis / Q000254:growth & development / Q000378:metabolism*
chemical_list: C043296:nickel-iron hydrogenase; D006864:Hydrogenase