Crystal Structure and Functional Characterization of Yeast YLR011wp, an Enzyme with NAD(P)H-FMN and Ferric Iron Reductase Activities

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Liger, Dominique | Graille, Marc | Zhou, Cong-Zhao | Leulliot, Nicolas | Quevillon-Cheruel, Sophie | Blondeau, Karine | Janin, Joël | van Tilbeurgh, Herman

Edité par CCSD ; American Society for Biochemistry and Molecular Biology -

International audience. Flavodoxins are involved in a variety of electron transfer reactions that are essential for life. Although FMN-binding proteins are well characterized in prokaryotic organisms, information is scarce for eukaryotic flavodoxins. We describe the 2.0-Å resolution crystal structure of the Saccharomyces cerevisiae YLR011w gene product, a predicted flavoprotein. YLR011wp indeed adopts a flavodoxin fold, binds the FMN cofactor, and self-associates as a homodimer. Despite the absence of the flavodoxin key fingerprint motif involved in FMN binding, YLR011wp binds this cofactor in a manner very analogous to classical flavodoxins. YLR011wp closest structural homologue is the homodimeric Bacillus subtilis Yhda protein (25% sequence identity) whose homodimer perfectly superimposes onto the YLR011wp one. Yhda, whose function is not documented, has 53% sequence identity with the Bacillus sp. OY1-2 azoreductase. We show that YLR011wp has an NAD(P)H-dependent FMN reductase and a strong ferricyanide reductase activity. We further demonstrate a weak but specific reductive activity on azo dyes and nitrocompounds.

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