title: Unraveling the electron transfer processes of a nanowire protein from Geobacter sulfurreducens.
abstract: The extracellular electron transfer metabolism of Geobacter sulfurreducens is sustained by several multiheme c-type cytochromes. One of these is the dodecaheme cytochrome GSU1996 that belongs to a new sub-class of c-type cytochromes. GSU1996 is composed by four similar triheme domains (A–D). The C-terminal half of the molecule encompasses the domains C and D, which are connected by a small linker and the N-terminal half of the protein contains two domains (A and B) that form one structural unit. It was proposed that this protein works as an electrically conductive device in G. sulfurreducens, transferring electrons within the periplasm or to outer-membrane cytochromes. In this work, a novel strategy was applied to characterize in detail the thermodynamic and kinetic properties of the hexaheme fragment CD of GSU1996. This characterization revealed the electron transfer process of GSU1996 for the first time, showing that a heme at the edge of the C-terminal of the protein is thermodynamic and kinetically competent to receive electrons from physiological redox partners. This information contributes towards understanding how this new sub-class of cytochromes functions as nanowires, and also increases the current knowledge of the extracellular electron transfer mechanisms in G. sulfurreducens.
authors.affiliation: Instituto de Tecnologia Química e Biológica - António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: Mónica N
authors.initials: MN
authors.lastname: Alves
authors.affiliation: Instituto de Tecnologia Química e Biológica - António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal; UCIBIO-Requimte, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal.
authors.forename: Ana P
authors.initials: AP
authors.lastname: Fernandes
authors.affiliation: UCIBIO-Requimte, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Caparica, Portugal.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Salgueiro
authors.affiliation: Instituto de Tecnologia Química e Biológica - António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal. Electronic address: cpaquete@itqb.unl.pt.
authors.forename: Catarina M
authors.initials: CM
authors.lastname: Paquete
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism; D004579:Electron Transport; D045302:Geobacter / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D053770:Nanowires; D017434:Protein Structure, Tertiary; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D045304:Cytochromes c
keywords: Electron transfer; Extracellular respiration; Geobacter; Multiheme cytochromes; Nanowires