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PDBsum entry 2gj3
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References listed in PDB file
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Key reference
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Title
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Structure of the redox sensor domain of azotobacter vinelandii nifl at atomic resolution: signaling, Dimerization, And mechanism.
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Authors
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J.Key,
M.Hefti,
E.B.Purcell,
K.Moffat.
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Ref.
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Biochemistry, 2007,
46,
3614-3623.
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PubMed id
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Abstract
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NifL is a multidomain sensor protein responsible for the transcriptional
regulation of genes involved in response to changes in cellular redox state and
ADP concentration. Cellular redox is monitored by the N-terminal PAS domain of
NifL which contains an FAD cofactor. Flavin-based PAS domains of this type have
also been referred to as LOV domains. To explore the mechanism of signal
recognition and transduction in NifL, we determined the crystal structure of the
FAD-bound PAS domain of NifL from Azotobacter vinelandii to 1.04 A resolution.
The structure reveals a novel cavity within the PAS domain which contains two
water molecules directly coordinated to the FAD. This cavity is connected to
solvent by multiple access channels which may facilitate the oxidation of the
FAD by molecular oxygen and the release of hydrogen peroxide. The structure
contains a dimer of the NifL PAS domain that is structurally very similar to
those described in other crystal structures of PAS domains and identifies a
conserved dimerization motif. An N-terminal amphipathic helix constitutes part
of the dimerization interface, and similar N-terminal helices are identified in
other PAS domain proteins. The structure suggests a model for redox-mediated
signaling in which a conformational change is initiated by redox-dependent
changes in protonation at the N5 atom of FAD that lead to reorganization of
hydrogen bonds within the flavin binding pocket. A structural signal is
subsequently transmitted to the beta-sheet interface between the monomers of the
PAS domain.
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