1QDB: Cytochrome C Nitrite Reductase

The enzyme cytochrome c nitrite reductase catalyses the six-electron reduction of nitrite to ammonia as one of the key steps in the biological nitrogen cycle, where it participates in the anaerobic energy metabolism of dissimilatory nitrate ammonification. Here we report on the crystal structure of this enzyme from the microorganism Sulfurospirillum deleyianum, which we solved by multiwavelength anomalous dispersion methods. We propose a reaction scheme for the transformation of nitrite based on structural and spectroscopic information. Cytochrome c nitrite reductase is a functional dimer, with 10 close-packed haem groups of type c and an unusual lysine-coordinated high-spin haem at the active site. By comparing the haem arrangement of this nitrite reductase with that of other multihaem cytochromes, we have been able to identify a family of proteins in which the orientation of haem groups is conserved whereas structure and function are not.
PDB ID: 1QDBDownload
MMDB ID: 10909
PDB Deposition Date: 1999/5/19
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 1.9  Å
Source Organism:
Similar Structures:
Biological Unit for 1QDB: dimeric; determined by author and by software (PISA)
Molecular Components in 1QDB
Label Count Molecule
Proteins (2 molecules)
Cytochrome C Nitrite Reductase
Molecule annotation
Chemicals (19 molecules)
* Click molecule labels to explore molecular sequence information.

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