title: Functional roles of CymA and NapC in reduction of nitrate and nitrite by Shewanella putrefaciens W3-18-1.
abstract: Shewanella putrefaciens W3-18-1 harbours two periplasmic nitrate reductase (Nap) gene clusters, NapC-associated nap-alpha (napEDABC) and CymA-dependent nap-beta (napDAGHB), for dissimilatory nitrate respiration. CymA is a member of the NapC/NirT quinol dehydrogenase family and acts as a hub to support different respiratory pathways, including those on iron [Fe(III)] and manganese [Mn(III, IV)] (hydr)oxide, nitrate, nitrite, fumarate and arsenate in Shewanella strains. However, in our analysis it was shown that another NapC/NirT family protein, NapC, was only involved in nitrate reduction, although both CymA and NapC can transfer quinol-derived electrons to a periplasmic terminal reductase or an electron acceptor. Furthermore, our results showed that NapC could only interact specifically with the Nap-alpha nitrate reductase while CymA could interact promiscuously with Nap-alpha, Nap-beta and the NrfA nitrite reductase for nitrate and nitrite reduction. To further explore the difference in specificity, site-directed mutagenesis on both CymA and NapC was conducted and the phenotypic changes in nitrate and nitrite reduction were tested. Our analyses demonstrated that the Lys-91 residue played a key role in nitrate reduction for quinol oxidation and the Asp-166 residue might influence the maturation of CymA. The Asp-97 residue might be one of the key factors that influence the interaction of CymA with the cytochromes NapB and NrfA.
authors.affiliation: Institute of hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China.|University of Chinese Academy of Sciences, Beijing 100049, PR China.
authors.forename: Hehong
authors.initials: H
authors.lastname: Wei
authors.affiliation: Institute of hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China.
authors.forename: Jingcheng
authors.initials: J
authors.lastname: Dai
authors.affiliation: Institute of hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China.|University of Chinese Academy of Sciences, Beijing 100049, PR China.
authors.forename: Ming
authors.initials: M
authors.lastname: Xia
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: Margaret F
authors.initials: MF
authors.lastname: Romine
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Shi
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: Alex
authors.initials: A
authors.lastname: Beliav
authors.affiliation: Center for Microbial Ecology, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Tiedje
authors.affiliation: Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Nealson
authors.affiliation: Pacific Northwest National Laboratory, Richland, WA 99354, USA.
authors.forename: James K
authors.initials: JK
authors.lastname: Fredrickson
authors.affiliation: Institute for Environmental Genomics and Department of Plant Biology and Microbiology, University of Oklahoma, OK, Norman, OK 73019, USA.
authors.forename: Jizhong
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Institute of hydrobiology, Chinese Academy of Sciences, Wuhan 430072, PR China.
authors.forename: Dongru
authors.initials: D
authors.lastname: Qiu
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D001224:Aspartic Acid / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D006873:Hydroquinones / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009565:Nitrate Reductases / Q000235:genetics*; D009566:Nitrates / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D016415:Sequence Alignment; D020614:Shewanella putrefaciens / Q000235:genetics / Q000378:metabolism*
chemical_list: D003574:Cytochrome c Group; D006873:Hydroquinones; D009566:Nitrates; D009573:Nitrites; D001224:Aspartic Acid; D009565:Nitrate Reductases; D008239:Lysine