title: A bacterial hydrogen-dependent CO2 reductase forms filamentous structures.
abstract: Interconversion of CO2 and formic acid is an important reaction in bacteria. A novel enzyme complex that directly utilizes molecular hydrogen as electron donor for the reversible reduction of CO2 has recently been identified in the Wood-Ljungdahl pathway of an acetogenic bacterium. This pathway is utilized for carbon fixation as well as energy conservation. Here we describe the further characterization of the quaternary structure of this enzyme complex and the unexpected behavior of this enzyme in polymerizing into filamentous structures. Polymerization of metabolic enzymes into similar structures has been observed only in rare cases but the increasing number of examples point towards a more general characteristic of enzyme functioning. Polymerization of the purified enzyme into ordered filaments of more than 0.1 μm in length was only dependent on the presence of divalent cations. Polymerization was a reversible process and connected to the enzymatic activity of the oxygen-sensitive enzyme with the filamentous form being the most active state.
authors.affiliation: Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Schuchmann
authors.affiliation: Department of Structural Biology, Max-Planck-Institute of Biophysics, Frankfurt am Main, Germany.
authors.forename: Janet
authors.initials: J
authors.lastname: Vonck
authors.affiliation: Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Müller
mesh_terms: D045855:Acetobacterium / Q000201:enzymology; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D055162:Biocatalysis; D002245:Carbon Dioxide / Q000378:metabolism*; D004795:Enzyme Stability; D005561:Formates / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism*; D007700:Kinetics; D008278:Magnesium Sulfate / Q000737:chemistry; D008854:Microscopy, Electron; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D055503:Protein Multimerization
chemical_list: D001426:Bacterial Proteins; D005561:Formates; C030544:formic acid; D002245:Carbon Dioxide; D008278:Magnesium Sulfate; D006859:Hydrogen; D010088:Oxidoreductases
keywords: acetogen; carbon dioxide reduction; carbon fixation; formate dehydrogenase; hydrogenase