The anatomy of a bifunctional enzyme: structural basis for reduction of oxygen to water and synthesis of nitric oxide by cytochrome cd1.
Cytochrome cd1-nitrite reductase is a bifunctional enzyme that catalyzes the one-electron reduction of nitrite to nitric oxide and the four-electron reduction of oxygen to water. The 1.55 A crystal structure of the dimeric enzyme from Thiosphaera pantotropha is reported here. The protein was sequenced from the X-ray structure. Each subunit contains a covalent c heme with two axial His ligands (His-17, His-69) and a unique noncovalent d1 heme ligated by Tyr-25 and His-200. The d1 heme is the mononuclear iron center where both oxygen and nitrite reduction take place. The two types of heme are located in separate domains whose arrangement suggests a mechanism requiring domain movement during catalysis.
Fülöp
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V
Laboratory of Molecular Biophysics, University of Oxford, England.
Moir
J W
JW
Ferguson
S J
SJ
Hajdu
J
J
D000595:Amino Acid Sequence; D001420:Bacteria, Aerobic / Q000201:enzymology*; D018360:Crystallography, X-Ray; D003574:Cytochrome c Group; D003580:Cytochromes / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D009572:Nitrite Reductases / Q000737:chemistry* / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation; D014867:Water / Q000378:metabolism
D003574:Cytochrome c Group; D003580:Cytochromes; D009097:Multienzyme Complexes; D009573:Nitrites; D014867:Water; D009569:Nitric Oxide; D006418:Heme; C019315:cytochrome cd1; D009572:Nitrite Reductases; D010100:Oxygen