Chromate reductase activity of the Paracoccus denitrificans ferric reductase B (FerB) protein and its physiological relevance
| Authors | |
|---|---|
| Year of publication | 2010 |
| Type | Article in Periodical |
| Magazine / Source | Archives of microbiology |
| MU Faculty or unit | |
| Citation | |
| Web | http://www.springerlink.com/content/l424530251550087/fulltext.pdf |
| Field | Biochemistry |
| Keywords | metal bioreduction; flavoenzyme; flavin radical; oxidative stress |
| Description | 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 (O2 absent) or higher than 2 (O2 present), the apparent KM value for chromate amounted to 70 uM with the maximum rate of 2.9 umol NADH /s/(mg protein). 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 sensitivity to antimycin suggests an involvement of the respiratory chain. |
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