Metal-metal bonding in biology: EXAFS evidence for a 2.5 A copper-copper bond in the CuA center of cytochrome oxidase.
Evidence for a direct Cu-Cu bond in the CuA center of cytochrome oxidase is reported. Simulation of the X-ray absorption spectrum of a recombinant CuA-binding domain of Bacillus subtilis cytochrome oxidase, and comparison with a structurally characterized directly-bonding Cu(1.5) ... Cu(1.5) inorganic complex, suggests that a Cu-Cu interaction of 2.5 +/- 0.1 A together with a short 2.2 A Cu-S interaction may be present in the CuA site. In light of these data, previous interpretations of the EXAFS of a number of cytochrome oxidase and nitrous oxide reductase enzymes which modeled the 2.6 A interaction as a long Cu-S(methionine) bond are possibly incorrect. A structural model based on the new data is presented which suggests that the CuA sites in cytochrome oxidase and N2O reductase are likely composed of a pair of modified type 1 copper centers with one histidine, one cysteine, and one weakly bound ligand (Met and/or Gln) joined by a Cu-Cu bond.
Blackburn
N J
NJ
Department of Chemistry Biochemistry, and Molecular Biology, Oregon Graduate Institute of Science and Technology, Portland 97291-1000.
Barr
M E
ME
Woodruff
W H
WH
van der Oost
J
J
de Vries
S
S
D001412:Bacillus subtilis / Q000201:enzymology; D001665:Binding Sites; D003300:Copper / Q000378:metabolism*; D004563:Electrochemistry; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism*; D008024:Ligands; D015394:Molecular Structure; D011487:Protein Conformation; D013052:Spectrometry, X-Ray Emission
D008024:Ligands; D003300:Copper; D003576:Electron Transport Complex IV