Atomic-resolution structure of nitric oxide reductase (cytochrome P450nor) reveals detailed intramolecular interactions in the protein molecule

The crystal structure of nitric oxide reductase, cytochrome P450nor (P450nor), has been determined at 1.0 Å resolution. P450nor consists of 403 amino acid residues (46 kDa), and is one of the largest proteins refined to this resolution so far. Owing to the atomic resolution, detailed intramolecular interactions, such as hydrogen bonds, multiple conformations of side chains, and anisotropic internal motions, are revealed in the structure. In addition, the accurate knowledge of the structures at atomic resolution enables us to examine general stereochemical parameters that are commonly used in refinement cycles of protein structures.