Chromate reductase activity of the Paracoccus denitrificans ferric reductase B (FerB) protein and its physiological relevance
Jazyk angličtina Země Německo Médium print-electronic
Typ dokumentu časopisecké články, práce podpořená grantem
- MeSH
- bakteriální proteiny genetika metabolismus MeSH
- chromany metabolismus MeSH
- flavinadenindinukleotid analogy a deriváty metabolismus MeSH
- flavoproteiny genetika metabolismus MeSH
- FMN-reduktasa genetika metabolismus MeSH
- koncentrace vodíkových iontů MeSH
- NAD metabolismus MeSH
- oxidace-redukce MeSH
- oxidační stres MeSH
- oxidoreduktasy genetika metabolismus MeSH
- Paracoccus denitrificans enzymologie genetika MeSH
- spotřeba kyslíku MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- bakteriální proteiny MeSH
- chromany MeSH
- chromate reductase MeSH Prohlížeč
- ferric citrate iron reductase MeSH Prohlížeč
- flavin semiquinone MeSH Prohlížeč
- flavinadenindinukleotid MeSH
- flavoproteiny MeSH
- FMN-reduktasa MeSH
- NAD MeSH
- oxidoreduktasy MeSH
The homodimeric flavoprotein FerB of Paracoccus denitrificans catalyzed the reduction of chromate with NADH as electron donor. When present, oxygen was reduced concomitantly with chromate. The recombinant enzyme had a maximum activity at pH 5.0. The stoichiometric ratio of NADH oxidized to chromate reduced was found to be 1.53 ± 0.09 (O(2) absent) or > 2 (O(2) present), the apparent K (M) value for chromate amounted to 70 ± 10 μM with the maximum rate of 2.9 ± 0.3 μmol NADH s(-1) (mg protein)(-1). Diode-array spectrophotometry and experiments with one-electron acceptors provided evidence for oxygen consumption being due to a flavin semiquinone, formed transiently during the interaction of FerB with chromate. At the whole-cell level, a ferB mutant strain displayed only slightly diminished rate of chromate reduction when compared to the wild-type parental strain. Anaerobically grown cells were more active than cells grown aerobically. The activity could be partly inhibited by antimycin, suggesting an involvement of the respiratory chain. Chromate concentrations above ten micromolars transiently slowed or halted culture growth, with the effect being more pronounced for the mutant strain. It appears, therefore, that, rather than directly reducing chromate, FerB confers a protection of cells against the oxidative stress accompanying chromate reduction. With a strain carrying the chromosomally integrated ferB promoter-lacZ fusion, it was shown that the ferB gene is not inducible by chromate.
Citace poskytuje Crossref.org
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