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PDBsum entry 3la2
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Transcription
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PDB id
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3la2
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References listed in PDB file
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Key reference
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Title
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Structural basis for the allosteric control of the global transcription factor ntca by the nitrogen starvation signal 2-Oxoglutarate.
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Authors
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M.X.Zhao,
Y.L.Jiang,
Y.X.He,
Y.F.Chen,
Y.B.Teng,
Y.Chen,
C.C.Zhang,
C.Z.Zhou.
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Ref.
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Proc Natl Acad Sci U S A, 2010,
107,
12487-12492.
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PubMed id
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Abstract
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2-oxogluatarate (2-OG), a metabolite of the highly conserved Krebs cycle, not
only plays a critical role in metabolism, but also constitutes a signaling
molecule in a variety of organisms ranging from bacteria to plants and animals.
In cyanobacteria, the accumulation of 2-OG constitutes the signal of nitrogen
starvation and NtcA, a global transcription factor, has been proposed as a
putative receptor for 2-OG. Here we present three crystal structures of NtcA
from the cyanobacterium Anabaena: the apoform, and two ligand-bound forms in
complex with either 2-OG or its analogue 2,2-difluoropentanedioic acid. All
structures assemble as homodimers, with each subunit composed of an N-terminal
effector-binding domain and a C-terminal DNA-binding domain connected by a long
helix (C-helix). The 2-OG binds to the effector-binding domain at a pocket
similar to that used by cAMP in catabolite activator protein, but with a
different pattern. Comparative structural analysis reveals a putative signal
transmission route upon 2-OG binding. A tighter coiled-coil conformation of the
two C-helices induced by 2-OG is crucial to maintain the proper distance between
the two F-helices for DNA recognition. Whereas catabolite activator protein
adopts a transition from off-to-on state upon cAMP binding, our structural
analysis explains well why NtcA can bind to DNA even in its apoform, and how
2-OG just enhances the DNA-binding activity of NtcA. These findings provided the
structural insights into the function of a global transcription factor regulated
by 2-OG, a metabolite standing at a crossroad between carbon and nitrogen
metabolisms.
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