Beschreibung:
<jats:title>ABSTRACT</jats:title>
<jats:p>
In
<jats:italic>Lactococcus lactis</jats:italic>
IL1403, 14 genes are under the control of the copper-inducible CopR repressor. This so-called CopR regulon encompasses the CopR regulator, two putative CPx-type copper ATPases, a copper chaperone, and 10 additional genes of unknown function. We addressed here the function of one of these genes,
<jats:italic>ytjD</jats:italic>
, which we renamed
<jats:italic>cinD</jats:italic>
(
<jats:underline>
<jats:underline>c</jats:underline>
</jats:underline>
opper-
<jats:underline>
<jats:underline>i</jats:underline>
</jats:underline>
nduced
<jats:underline>
<jats:underline>n</jats:underline>
</jats:underline>
itroreductase). Copper, cadmium, and silver induced
<jats:italic>cinD in vivo</jats:italic>
, as shown by real-time quantitative PCR. A knockout mutant of
<jats:italic>cinD</jats:italic>
was more sensitive to oxidative stress exerted by 4-nitroquinoline-
<jats:italic>N</jats:italic>
-oxide and copper. Purified CinD is a flavoprotein and reduced 2,6-dichlorophenolindophenol and 4-nitroquinoline-
<jats:italic>N</jats:italic>
-oxide with
<jats:italic>k</jats:italic>
<jats:sub>cat</jats:sub>
values of 27 and 11 s
<jats:sup>−1</jats:sup>
, respectively, using NADH as a reductant. CinD also exhibited significant catalase activity
<jats:italic>in vitro</jats:italic>
. The X-ray structure of CinD was resolved at 1.35 Å and resembles those of other nitroreductases. CinD is thus a nitroreductase which can protect
<jats:italic>L. lactis</jats:italic>
against oxidative stress that could be exerted by nitroaromatic compounds and copper.
</jats:p>