ORGANIZATION OF THE HAO GENE-CLUSTER OF NITROSOMONAS-EUROPAEA - GENESFOR 2 TETRAHEME C-CYTOCHROMES

The organization of genes for three proteins involved in ammonia oxida tion in Nitrosomonas europaea has been investigated. The amino acid se quence of the N-terminal region and four heme-containing peptides prod uced by proteolysis of the tetraheme; cytochrome c(554) of N. europaea were determined by Edman degradation. The gene (cycA) encoding this c ytochrome is present in three copies per genome (H. McTavish, F. LaQui er, D. Arciero, M. Logan, G. Mundfrom, J. A. Fuchs, and A. B. Hooper, J. Bacteriol. 175:2445-2447, 1993). Three clones, representing at leas t two copies of cycA, were isolated and sequenced by the dideoxy-chain termination procedure. In both copies, the sequences of 211 amino aci ds derived from the gene sequence are identical and include all amino acids predicted by the proteolytic peptides. In two copies, the cycA o pen reading frame (ORF) is followed closely (three bases in one copy) by a second ORF predicted to encode a 28-kDa tetraheme c cytochrome no t previously characterized but similar to the nirT gene product of Pse udomonas stutzeri. In one copy of the cycA gene cluster, the second OR F is absent.