Cytochrome c nitrite reductase from Wolinella succinogenes. Structure at 1.6 A resolution, inhibitor binding, and heme-packing motifs

• Published in: The Journal of biological chemistry Vol. 275; no. 50; pp. 39608 - 39616
• Main Authors: Einsle, O, Stach, P, Messerschmidt, A, Simon, J, Kröger, A, Huber, R, Kroneck, P M
• Format: Journal Article
• Language: English
• Published: United States 15-12-2000
• Subjects: Amino Acid Motifs; Amino Acid Sequence; Azides - chemistry; Binding Sites; Calcium - metabolism; Conserved Sequence; Crystallography, X-Ray; Cytochromes a1; Cytochromes c1; Dimerization; Heme - chemistry; Iron - chemistry; Ligands; Models, Biological; Models, Molecular; Molecular Sequence Data; Multigene Family; Nitrate Reductases - chemistry; Phylogeny; Protein Binding; Protein Conformation; Protein Structure, Secondary; Sequence Homology, Amino Acid; Sulfates - chemistry; Water; Wolinella - enzymology
• ISSN: 0021-9258
• DOI: 10.1074/jbc.M006188200

Cytochrome c nitrite reductase catalyzes the 6-electron reduction of nitrite to ammonia. This second part of the respiratory pathway of nitrate ammonification is a key step in the biological nitrogen cycle. The x-ray structure of the enzyme from the epsilon-proteobacterium Wolinella succinogenes has been solved to a resolution of 1.6 A. It is a pentaheme c-type cytochrome whose heme groups are packed in characteristic motifs that also occur in other multiheme cytochromes. Structures of W. succinogenes nitrite reductase have been obtained with water bound to the active site heme iron as well as complexes with two inhibitors, sulfate and azide, whose binding modes and inhibitory functions differ significantly. Cytochrome c nitrite reductase is part of a highly optimized respiratory system found in a wide range of Gram-negative bacteria. It reduces both anionic and neutral substrates at the distal side of a lysine-coordinated high-spin heme group, which is accessible through two different channels, allowing for a guided flow of reaction educt and product. Based on sequence comparison and secondary structure prediction, we have demonstrated that cytochrome c nitrite reductases constitute a protein family of high structural similarity.