Cytochrome P460 and hydroxyamine oxidoreductase of Nitrosomonas europaea both catalyze the oxidation of hydroxylamine and contain a 460 nm-absorbing chromophore. The gene (cyp) encoding cytochrome P460 was cloned and sequenced. The predicted amino acid sequence contains a single c-heme binding motif (CXXCH) near the carboxy-terminus. Cytochrome P460 shows little sequence homology to other c-cytochromes including hydroxyamine oxidoreductase. The presence of a signal peptide and a possible c-heme binding site suggest that the cytochrome P460 of N. europaea is periplasmic.