moaR, a gene that encodes a positive regulator of the monoamine regulon in Klebsiella aerogenes

Abstract

We cloned and sequenced a Klebsiella 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 of K. aerogenes was disrupted by homologous recombination with a plasmid containing the inactivated moaR. The resultant mutant showed the same phenotype as previously isolated atsT mutant strains that are negative for the derepressed synthesis of arylsulfatase. In this mutant strain, tyramine also failed to induce the synthesis of tyramine oxidase or the production of a 30-kDa protein. The moaR gene is capable of encoding a protein of 26,238 Da. The putative MoaR protein has a helix-turn-helix motif in its C terminus. Thus, it seems likely that the MoaR protein regulates the operons by binding to the regulatory region of the monoamine regulon. The MoaR protein is subject to autogenous control, which was shown by use of a moaR'-lacZ transcriptional fusion.