title: A protein trisulfide couples dissimilatory sulfate reduction to energy conservation.
abstract: Microbial sulfate reduction has governed Earth's biogeochemical sulfur cycle for at least 2.5 billion years. However, the enzymatic mechanisms behind this pathway are incompletely understood, particularly for the reduction of sulfite-a key intermediate in the pathway. This critical reaction is performed by DsrAB, a widespread enzyme also involved in other dissimilatory sulfur metabolisms. Using in vitro assays with an archaeal DsrAB, supported with genetic experiments in a bacterial system, we show that the product of sulfite reduction by DsrAB is a protein-based trisulfide, in which a sulfite-derived sulfur is bridging two conserved cysteines of DsrC. Physiological studies also reveal that sulfate reduction rates are determined by cellular levels of DsrC. Dissimilatory sulfate reduction couples the four-electron reduction of the DsrC trisulfide to energy conservation.
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: André A
authors.initials: AA
authors.lastname: Santos
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: Sofia S
authors.initials: SS
authors.lastname: Venceslau
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.
authors.forename: Fabian
authors.initials: F
authors.lastname: Grein
authors.affiliation: Department of Earth and Planetary Science, Harvard University, Cambridge, MA, USA.
authors.forename: William D
authors.initials: WD
authors.lastname: Leavitt
authors.affiliation: Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Dahl
authors.affiliation: Department of Earth and Planetary Science, Harvard University, Cambridge, MA, USA.
authors.forename: David T
authors.initials: DT
authors.lastname: Johnston
authors.affiliation: Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal. ipereira@itqb.unl.pt.
authors.forename: Inês A C
authors.initials: IA
authors.lastname: Pereira
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry / Q000378:metabolism*; D019611:Archaeoglobus fulgidus / Q000201:enzymology*; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D004734:Energy Metabolism; D010084:Oxidation-Reduction; D011506:Proteins / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism; D013440:Sulfides / Q000737:chemistry / Q000378:metabolism*; D013447:Sulfites / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*
chemical_list: D019843:Archaeal Proteins; D011506:Proteins; D013431:Sulfates; D013440:Sulfides; D013447:Sulfites; D013455:Sulfur; D003545:Cysteine