The crystal structure of CYP55A1 has appeared in Nature Structural Biology volume 4, number 10, October 1997 pp. 827-832. This enzyme is a nitric oxide reductase. The source is fungal (Fusarium oxysporum), though the protein is soluble and falls in phylogenetic trees in the 105 family. This probably represents a lateral gene transfer from a bacterial species like Streptomyces. .