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A molecular approach to the bioenergetics of sulfate reduction

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The dissimilation of sulfur compounds is likely to have been one of the first energy metabolisms on the early Earth [1]. However, many questions remain about how sulfur-metabolizing organisms obtain energy for growth from reducing, oxidizing or disproportionating sulfur compounds. In the case of sulfate reduction, the terminal reductases involved (APS reductase, AprAB, and dissimilatory sulfite reductase, DsrAB) have long been identified, but how these two reactions are coupled to energy conservation is still not clear. DsrAB, in particular, is a key enzyme in dissimilatory sulfur metabolism, being present not only sulfate/thiosulfate/sulfite reducing organisms, but also in sulfur-oxidizers and sulfur disproportionators. Our lab has studied several of the key proteins involved in sulfate reduction, including AprAB, DsrAB and two respiratory membrane complexes specific to sulfur-metabolizing organisms, QmoABC and DsrMKJOP, which are involved in the electron transfer pathways with AprAB and DsrAB [2]. These complexes hint at the possibility of menaquinone involvement and chemiosmotic energy conservation, during sulfate reduction. In addition, a genomic analysis of energy metabolism genes in sulfate reducers suggested that the recently recognized process of electron bifurcation may also be involved [3], and that there are conspicuous links between sulfate reducers and methanogenic organisms [1]. In this talk I will present an overview of the role of these proteins in sulfate reduction, with a special focus on the function of the small protein DsrC as a physiological partner of DsrAB and the DsrMKJOP complex [4]. 1- Sousa,F.L., Thiergart, T., Landan, G., Nelson-Sathi,S., Pereira, I.A.C., Allen, J.F., Lane,N., Martin, W. F. (2013) Early bioenergetic evolution. Phil Trans R Soc B, 368, 20130088 2- Grein F, Ramos AR, Venceslau SS, Pereira IAC . (2013) Unifying concepts in anaerobic respiration: Insights from dissimilatory sulfur metabolism. Biochim Biophys Acta.-Bioenergetics 1827 145-160 3- Pereira IAC , Ramos AR, Grein F, Marques MC, Da Silva SM and Venceslau SS (2011). A comparative genomic analysis of energy metabolism in sulfate reducing bacteria and archaea. Front. Microbiol. 2:69 4- Venceslau SS, Stockdreher Y, Dahl C, Pereira IAC . (2014) The “bacterial heterodisulfide” DsrC is a key protein in dissimilatory sulfur metabolism, Biochim. Biophys. Acta-Bioenergetics 1837, 1148-1164

This talk is part of the Department of Earth Sciences Seminars (downtown) series.

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