[SCAN Highlight] A protein trisulfide couples dissimilatory sulfate reduction to energy conservation

SCAN Paper Highlight

Title: A protein trisulfide couples dissimilatory sulfate reduction to energy conservation

Speaker: Inês Cardoso Pereira

Affiliation: Bacterial Energy Metabolism Lab

Abstract:

Microbial sulfate reduction has governed the Earth's biogeochemical sulfur cycle for at least 2.5 billion years.  However, the enzymatic mechanisms behind this pathway are incompletely understood, particularly for 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, where 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 4-electron reduction of the DsrC trisulfide to energy conservation.