Molecular mechanism of energy conservation in polysulfide respiration

Abstract

Bacterial polysulfide reductase (PsrABC) is an integral membrane protein complex responsible for quinone-coupled reduction of polysulfide, a process important in extreme environments such as deep-sea vents and hot springs. We determined the structure of polysulfide reductase from Thermus thermophilus at 2.4-A resolution, revealing how the PsrA subunit recognizes and reduces its unique polyanionic substrate. The integral membrane subunit PsrC was characterized using the natural substrate menaquinone-7 and inhibitors, providing a comprehensive representation of a quinone binding site and revealing the presence of a water-filled cavity connecting the quinone binding site on the periplasmic side to the cytoplasm. These results suggest that polysulfide reductase could be a key energy-conserving enzyme of the T. thermophilus respiratory chain, using polysulfide as the terminal electron acceptor and pumping protons across the membrane via a previously unknown mechanism.

A Molybdopterin Oxidoreductase Is Involved in H 2 Oxidation in Desulfovibrio desulfuricans G20

“…Some Psr proteins do not contain any hemes in the membrane-bound subunit, unlike many other heme b-containing membrane-bound bis-MGD enzymes. However, these Psrs still bind quinone or its analogs (17). Quinone-binding sites are difficult to identify at the sequence level due to the limited number of quinone-binding structures available and the diversity of quinone-binding proteins (33).…”

“…Bis-MGD proteins with the highest degrees of similarity to G20 Mop include the Mop in D. vulgaris strain Hildenborough, polysulfide reductase (NrfD) in "Desulfococcus oleovorans" Hxd3 and "Solibacter usitatus" Ellin6076, and nitrate reductase in Geobacter uraniireducens Rf4. Orthologous polysulfide reductases and nitrate reductases whose crystal structures have been studied have a transmembrane subunit which may interact with menaquinone during electron transfer (16,17). The cellular location of the MopABCD complex of strain G20 was determined in silico using PSORT-B (12) and CELLO II (40).…”

Biochemical Characterization of Individual Components of the Allochromatium vinosum DsrMKJOP Transmembrane Complex Aids Understanding of Complex Function In Vivo

“…The identification of DsrP as a b-type cytochrome is highly remarkable since, to the best of our knowledge, DsrP provides the first experimental evidence for heme binding in the NrfD/PsrC family. The first structure of a protein from this family, PsrC from Thermus thermophilus, shows that it does not contain heme (19). The only NrfD/PsrC family member for which heme binding has been debated on the basis of sequence analysis is HybB, the membrane subunit of hydrogenase 2 from E. coli (9,31).…”

Correct Assembly of Iron-Sulfur Cluster FS0 into Escherichia coli Dimethyl Sulfoxide Reductase (DmsABC) Is a Prerequisite for Molybdenum Cofactor Insertion

“…Dimethyl sulfoxide reductase (DmsABC) is a terminal reductase that reduces dimethyl sulfoxide to dimethyl sulfide (3). It is a member of the bacterial CISM (complex iron-sulfur molybdoenzyme) family that includes E. coli formate dehydrogenases (FdnGHI and FdoGHI) (2,4,5), E. coli nitrate reductases (NarGHI and Nar-ZYV) (6,7), Salmonella typhimurium thiosulfate reductase (PhsABC) (8), and the Wolinella succinogenes and Thermus thermophilus (PsrABC) polysulfide reductases (9,10). This family of enzymes contributes to the broad metabolic diversity that permits bacterial growth utilizing a wide range of respiratory substrates.…”