bi6b00699_si_001.pdf (7.51 MB)
Activation of the Class Ib Ribonucleotide Reductase by a Flavodoxin Reductase in Bacillus cereus
journal contribution
posted on 2016-08-25, 00:00 authored by Marie Lofstad, Ingvild Gudim, Marta Hammerstad, Åsmund
Kjendseth Røhr, Hans-Petter HerslethTo reduce ribonucleotides to deoxyribonucleotides,
the manganese-bound
form of class Ib ribonucleotide reductase (RNR) must be activated
via a pathway that involves redox protein(s). The reduced flavoprotein
NrdI is an important protein in this pathway, as it reduces dioxygen
to superoxide. Superoxide then reacts with the RNR MnII2 site to generate a tyrosyl radical that is required
for catalysis. A native NrdI reductase has not yet been identified.
We herein demonstrate through kinetic and spectroscopic studies that
an endogenous flavodoxin reductase can function as the NrdI reductase
in Bacillus cereus. When the flavodoxin reductase
reduces NrdI, tyrosyl radical formation in RNR is promoted under aerobic
conditions, significantly increasing the radical yield. Thus, a missing
piece of the class Ib RNR NrdI redox pathway has finally been identified.