Beschreibung:
<jats:title>ABSTRACT</jats:title>
<jats:p>
Chromatin immunoprecipitation and microarray (ChIP-chip) analysis showed that the nitric oxide (NO)-sensitive repressor NsrR from
<jats:italic>Escherichia coli</jats:italic>
binds in vivo to the promoters of the
<jats:italic>tynA</jats:italic>
and
<jats:italic>feaB</jats:italic>
genes. These genes encode the first two enzymes of a pathway that is required for the catabolism of phenylethylamine (PEA) and its hydroxylated derivatives tyramine and dopamine. Deletion of
<jats:italic>nsrR</jats:italic>
caused small increases in the activities of the
<jats:italic>tynA</jats:italic>
and
<jats:italic>feaB</jats:italic>
promoters in cultures grown on PEA. Overexpression of
<jats:italic>nsrR</jats:italic>
severely retarded growth on PEA and caused a marked repression of the
<jats:italic>tynA</jats:italic>
and
<jats:italic>feaB</jats:italic>
promoters. Both the growth defect and the promoter repression were reversed in the presence of a source of NO. These results are consistent with NsrR mediating repression of the
<jats:italic>tynA</jats:italic>
and
<jats:italic>feaB</jats:italic>
genes by binding (in an NO-sensitive fashion) to the sites identified by ChIP-chip.
<jats:italic>E. coli</jats:italic>
was shown to use 3-nitrotyramine as a nitrogen source for growth, conditions which partially induce the
<jats:italic>tynA</jats:italic>
and
<jats:italic>feaB</jats:italic>
promoters. Mutation of
<jats:italic>tynA</jats:italic>
(but not
<jats:italic>feaB</jats:italic>
) prevented growth on 3-nitrotyramine. Growth yields, mutant phenotypes, and analyses of culture supernatants suggested that 3-nitrotyramine is oxidized to 4-hydroxy-3-nitrophenylacetate, with growth occurring at the expense of the amino group of 3-nitrotyramine. Accordingly, enzyme assays showed that 3-nitrotyramine and its oxidation product (4-hydroxy-3-nitrophenylacetaldehyde) could be oxidized by the enzymes encoded by
<jats:italic>tynA</jats:italic>
and
<jats:italic>feaB</jats:italic>
, respectively. The results suggest that an additional physiological role of the PEA catabolic pathway is to metabolize nitroaromatic compounds that may accumulate in cells exposed to NO.
</jats:p>