The structural gene for copper-and topa quinone-containing monoamine oxidase (maoA) and an unknown amine oxidase gene have been located at 30.9 min on the Escherichia coli chromosome. Deletion analysis showed that the unknown gene was located within a 1.1-kb cloned fragment adjacent to the maoA gene. The nucleotide sequence of this fragment was determined, and a single open reading frame (maoB) consisting of 903 bp was found. The gene encoded a polypeptide with a predicted molecular mass of 34,619 Da which was correlated with the migration on a sodium dodecyl sulfate-polyacrylamide gel. The predicted amino acid sequence of the MaoB protein was identical to the NH 2 -terminal amino acid sequence derived by Edman degradation of the protein synthesized under the self-promoter. No homology of the nucleotide sequence of maoB to the sequences of any reported genes was found. However, the amino acid sequence of MaoB showed a high level of homology with respect to the helix-turn-helix motif of the AraC family in its C terminus. The homology search and disruption of maoA on the chromosome led to the conclusion that MaoB is a transcriptional activator of maoA but not an amine oxidase. The consensus sequence of the cyclic AMP-cyclic AMP receptor protein complex binding domain was adjacent to the putative promoter for the maoB gene. By use of lac gene fusions with the maoA and maoB genes, we showed that the maoA gene is regulated by tyramine and MaoB and that the expression of the maoB gene is subject to catabolite repression. Thus, it seems likely that tyramine and the MaoB protein activate the transcription of maoA by binding to the regulatory region of the maoA gene.

We cloned and sequenced a KiebsieUla aerogenes gene (moaR) for activation of arylsulfatase synthesis by tyramine. This gene was cloned by complementation of a K. aerogenes mutant in which tyramine fails to relieve the arylsulfatase repression caused by sulfur compounds. The moaR gene also activated induction of the synthesis of both tyramine oxidase and the 30-kDa protein that is specifically induced by high concentrations of tyramine or catecholamines. The moaR gene on the chromosome of the wild-type strain ofK. aerogenes was disrupted by homologous recombination with a plasmid containing the inactivated moaR. The resultant mutant

A 30-kDa protein accumulated upon induction by a high concentration of tyramine or dopamine in cells of Klebsiella aerogenes (Ka). These cells carried a plasmid (pAS123) that included the arylsulfatase operon (atsBA). Deletion analysis showed that the region essential for induction of the 30-kDa protein was located within a 2.0-kb cloned segment downstream of the atsBA operon. The nucleotide (nt) sequence of the 2.0-kb fragment revealed two open reading frames (ORFs), moaE and moaF. Transcription from a putative promoter of moaE was induced by the addition of tyramine, and the moaF gene was co-transcribed from this monoamine-inducible Ka promoter. The deduced Ka MoaE protein was homologous to insect-type alcohol dehydrogenase. The sequence of the 18 amino acids from the N-terminus of the purified 30-kDa protein agreed with that deduced from the nt sequence of moaF. Using a Ka strain with a mutant moaR gene, we found that MoaR, that acts as the positive regulator of the monoamine regulon, also acts as the positive regulator of the moaEF operon.