4PTZ

Crystal structure of the Escherichia coli alkanesulfonate FMN reductase SsuE in FMN-bound form

Summary for 4PTZ

• Entry DOI: 10.2210/pdb4ptz/pdb
• Related: 4PTY 4PU0
• Descriptor: FMN reductase SsuE, FLAVIN MONONUCLEOTIDE, GLYCEROL, ... (5 entities in total)
• Functional Keywords: flavodoxin-like fold, nadph-dependent fmn reductase, ssud, oxidoreductase
• Biological source: Escherichia coli
• Total number of polymer chains: 4
• Total formula weight: 89139.21

Authors

Driggers, C.M.,Ellis, H.R.,Karplus, P.A. (deposition date: 2014-03-11, release date: 2014-06-18, Last modification date: 2024-04-03)

Primary citation

Driggers, C.M.,Dayal, P.V.,Ellis, H.R.,Karplus, P.A.
Crystal Structure of Escherichia coli SsuE: Defining a General Catalytic Cycle for FMN Reductases of the Flavodoxin-like Superfamily.
Biochemistry, 53:3509-3519, 2014

PubMed Abstract: The Escherichia coli sulfur starvation utilization (ssu) operon includes a two-component monooxygenase system consisting of a nicotinamide adenine dinucleotide phosphate (NADPH)-dependent flavin mononucleotide (FMN) reductase, SsuE, and a monooxygenase, SsuD. SsuE is part of the flavodoxin-like superfamily, and we report here the crystal structures of its apo, FMN-bound, and FMNH2-bound forms at ∼2 Å resolution. In the crystals, SsuE forms a tetramer that is a dimer of dimers similar to those seen for homologous FMN reductases, quinone reductases, and the WrbA family of enzymes. A π-helix present at the tetramer building interface is unique to the reductases from two-component monooxygenase systems. Analytical ultracentrifugation studies of SsuE confirm a dimer-tetramer equilibrium exists in solution, with FMN binding favoring the dimer. As the active site includes residues from both subunits, at least a dimeric association is required for the function of SsuE. The structures show that one FMN binds tightly in a deeply held site, which makes available a second binding site, in which either a second FMN or the nicotinamide of NADPH can bind. The FMNH2-bound structure shows subtle changes consistent with its binding being weaker than that of FMN. Combining this information with published kinetic studies, we propose a general catalytic cycle for two-component reductases of the flavodoxin-like superfamily, by which the enzyme can potentially provide FMNH2 to its partner monooxygenase by different routes depending on the FMN concentration and the presence of a partner monooxygenase.

PubMed: 24816272
DOI: 10.1021/bi500314f

Experimental method

X-RAY DIFFRACTION (1.9007 Å)