1L0V: Quinol-Fumarate Reductase With Menaquinol Molecules

Citation:
Abstract
The quinol-fumarate reductase (QFR) respiratory complex of Escherichia coli is a four-subunit integral-membrane complex that catalyzes the final step of anaerobic respiration when fumarate is the terminal electron acceptor. The membrane-soluble redox-active molecule menaquinol (MQH(2)) transfers electrons to QFR by binding directly to the membrane-spanning region. The crystal structure of QFR contains two quinone species, presumably MQH(2), bound to the transmembrane-spanning region. The binding sites for the two quinone molecules are termed Q(P) and Q(D), indicating their positions proximal (Q(P)) or distal (Q(D)) to the site of fumarate reduction in the hydrophilic flavoprotein and iron-sulfur protein subunits. It has not been established whether both of these sites are mechanistically significant. Co-crystallization studies of the E. coli QFR with the known quinol-binding site inhibitors 2-heptyl-4-hydroxyquinoline-N-oxide and 2-[1-(p-chlorophenyl)ethyl] 4,6-dinitrophenol establish that both inhibitors block the binding of MQH(2) at the Q(P) site. In the structures with the inhibitor bound at Q(P), no density is observed at Q(D), which suggests that the occupancy of this site can vary and argues against a structurally obligatory role for quinol binding to Q(D). A comparison of the Q(P) site of the E. coli enzyme with quinone-binding sites in other respiratory enzymes shows that an acidic residue is structurally conserved. This acidic residue, Glu-C29, in the E. coli enzyme may act as a proton shuttle from the quinol during enzyme turnover.
PDB ID: 1L0VDownload
MMDB ID: 19091
PDB Deposition Date: 2002/2/13
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 3.3  Å
Source Organism:
Similar Structures:
Biological Unit for 1L0V: tetrameric; determined by author and by software (PISA)
Molecular Components in 1L0V
Label Count Molecule
Proteins (4 molecules)
1
Fumarate Reductase Flavoprotein Subunit(Gene symbol: frdA)
Molecule annotation
1
Fumarate Reductase Iron-sulfur Protein(Gene symbol: frdB)
Molecule annotation
1
Fumarate Reductase 15 KDA Hydrophobic Protein(Gene symbol: frdC)
Molecule annotation
1
Fumarate Reductase 13 KDA Hydrophobic Protein(Gene symbol: frdD)
Molecule annotation
Chemicals (9 molecules)
1
1
2
1
3
1
4
1
5
1
6
2
7
2
* Click molecule labels to explore molecular sequence information.

Citing MMDB
.