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PDBsum entry 1drm
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Contents |
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* Residue conservation analysis
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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 a biological oxygen sensor: a new mechanism for heme-Driven signal transduction.
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Authors
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W.Gong,
B.Hao,
S.S.Mansy,
G.Gonzalez,
M.A.Gilles-Gonzalez,
M.K.Chan.
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Ref.
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Proc Natl Acad Sci U S A, 1998,
95,
15177-15182.
[DOI no: ]
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PubMed id
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Abstract
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The FixL proteins are biological oxygen sensors that restrict the expression of
specific genes to hypoxic conditions. FixL's oxygen-detecting domain is a heme
binding region that controls the activity of an attached histidine kinase. The
FixL switch is regulated by binding of oxygen and other strong-field ligands. In
the absence of bound ligand, the heme domain permits kinase activity. In the
presence of bound ligand, this domain turns off kinase activity. Comparison of
the structures of two forms of the Bradyrhizobium japonicum FixL heme domain,
one in the "on" state without bound ligand and one in the
"off" state with bound cyanide, reveals a mechanism of regulation by a
heme that is distinct from the classical hemoglobin models. The close structural
resemblance of the FixL heme domain to the photoactive yellow protein confirms
the existence of a PAS structural motif but reveals the presence of an
alternative regulatory gateway.
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Figure 3.
Fig. 3. Ball-and-stick diagrams of three heme-binding
pockets. Structures are shown for Glycera dibranchiata
hemoglobin (PDB ID: 2HBG) (Left), BjFixLH (Center), and the NO
transporter protein (PDB ID: 1NP1) (Right) (27, 28). The
rightmost and leftmost side chains correspond to the E7 and E11
residues of hemoglobins, respectively. The additional side chain
in BjFixLH (red) corresponds to Ile 215. The structures were
aligned based on the orientation of the proximal histidine and
the porphyrin ring. The atoms are colored as in Fig. 1.
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Figure 5.
Fig. 5. Comparison of the structures of the regulatory FG
loop of BjFixLH in the unliganded "on" and cyanide bound "off"
states. (A) The structure of the FG loop in the met-BjFixLH
(brown) illustrating the hydrogen-bonding interactions (Left)
and 2F[O]-F[C] electron density map (1  ) (Right).
(B) Corresponding figure for cyanomet-BjFixLH (blue) showing
hydrogen bonding (Left) and electron density (Right). (C)
Stereoview of overlap of the refined models for both states.
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