Molecular mechanism of energy conservation in polysulfide respiration.
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.
Department of Biophysics, University of New South Wales, Barker Street, Sydney, New South Wales 2052, Australia. m.jormakka@centenary.org.au
Mika
M
Jormakka
Ken
K
Yokoyama
Takahiro
T
Yano
Masatada
M
Tamakoshi
Satoru
S
Akimoto
Tatsuro
T
Shimamura
Paul
P
Curmi
So
S
Iwata
D001665:Binding Sites; D020134:Catalytic Domain; D002462:Cell Membrane / Q000201:enzymology; D019281:Dimerization; D004579:Electron Transport; D004583:Electrons; D004734:Energy Metabolism; D008958:Models, Molecular; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011522:Protons; D011809:Quinones / Q000378:metabolism; D055672:Static Electricity; D013440:Sulfides / Q000378:metabolism*; D016963:Thermus thermophilus / Q000201:enzymology*
D021122:Protein Subunits; D011522:Protons; D011809:Quinones; D013440:Sulfides; C032915:polysulfide; D010088:Oxidoreductases; C074883:polysulfide reductase