Chromate reductase activity of the Paracoccus denitrificans ferric reductase B (FerB) protein and its physiological relevance

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Authors

SEDLÁČEK Vojtěch KUČERA Igor

Year of publication 2010
Type Article in Periodical
Magazine / Source Archives of microbiology
MU Faculty or unit

Faculty of Science

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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