title: The roles of hydrogenases 3 and 4, and the F0F1-ATPase, in H2 production by Escherichia coli at alkaline and acidic pH.
abstract: The hyc operon of Escherichia coli encodes the H2-evolving hydrogenase 3 (Hyd-3) complex that, in conjunction with formate dehydrogenase H (Fdh-H), constitutes a membrane-associated formate hydrogenlyase (FHL) catalyzing the disproportionation of formate to CO2 and H2 during fermentative growth at low pH. Recently, an operon (hyf) encoding a potential second H2-evolving hydrogenase (Hyd-4) was identified in E. coli. In this study the roles of the hyc- and hyf-encoded systems in formate-dependent H2 production and Fdh-H activity have been investigated. In cells grown on glucose under fermentative conditions at slightly acidic pH the production of H2 was mostly Hyd-3- and Fdh-H-dependent, and Fdh-H activity was also mainly Hyd-3-dependent. However, at slightly alkaline pH, H2 production was found to be largely Hyd-4, Fdh-H and F0F1-ATPase-dependent, and Fdh-H activity was partially dependent on Hyd-4 and F0F1-ATPase. These results suggest that, at slightly alkaline pH, H2 production and Fdh-H activity are dependent on both the F0F1-ATPase and a novel FHL, designated FHL-2, which is composed of Hyd-4 and Fdh-H, and is driven by a proton gradient established by the F0F1-ATPase.
authors.affiliation: Department of Biophysics of the Biological Faculty, Yerevan State University, 1 Alex Manougian Street, 375049, Yerevan, Armenia.
authors.forename: Karine
authors.initials: K
authors.lastname: Bagramyan
authors.forename: Nelli
authors.initials: N
authors.lastname: Mnatsakanyan
authors.forename: Anna
authors.initials: A
authors.lastname: Poladian
authors.forename: Anait
authors.initials: A
authors.lastname: Vassilian
authors.forename: Armen
authors.initials: A
authors.lastname: Trchounian
mesh_terms: D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D005560:Formate Dehydrogenases / Q000235:genetics / Q000378:metabolism*; D005798:Genes, Bacterial; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006864:Hydrogenase / Q000235:genetics / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D011523:Protoplasts / Q000378:metabolism
chemical_list: D009097:Multienzyme Complexes; D006859:Hydrogen; D006864:Hydrogenase; D005560:Formate Dehydrogenases; C054017:formate hydrogenlyase; D006180:Proton-Translocating ATPases