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PDBsum entry 1eqd
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Signaling protein
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PDB id
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1eqd
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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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Nitric oxide binding to nitrophorin 4 induces complete distal pocket burial.
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Authors
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A.Weichsel,
J.F.Andersen,
S.A.Roberts,
W.R.Montfort.
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Ref.
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Nat Struct Biol, 2000,
7,
551-554.
[DOI no: ]
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PubMed id
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Abstract
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The nitrophorins comprise an unusual family of proteins that use ferric
(Fe(III)) heme to transport highly reactive nitric oxide (NO) from the salivary
gland of a blood sucking bug to the victim, resulting in vasodilation and
reduced blood coagulation. We have determined structures of nitrophorin 4 in
complexes with H2O, cyanide and nitric oxide. These structures reveal a
remarkable feature: the nitrophorins have a broadly open distal pocket in the
absence of NO, but upon NO binding, three or more water molecules are expelled
and two loops fold into the distal pocket, resulting in the packing of
hydrophobic groups around the NO molecule and increased distortion of the heme.
In this way, the protein apparently forms a 'hydrophobic trap' for the NO
molecule. The structures are very accurate, ranging between 1.6 and 1.4 A
resolutions.
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Figure 3.
Figure 3. Loop ordering on NO binding. Space filling views of
the distal pockets in the NP4 -NO (left) and NP4 -CN- (right)
structures. The view is from above the distal pocket, with heme
shown in black, heme oxygens in orange, NO in magenta, CN- in
cyan, five water molecules in red, and loops A-B and G-H in
green. Binding of NO leads to reordering of the A-B and G-H
loops, expulsion of the water molecules, burying of NO and Asp
30, and packing of Leu 130 against the NO molecule.
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Figure 4.
Figure 4. Hydrogen bonding in the mobile loops. a, Stereo
view of the distal pocket in NP4 -NO. b, Stereo view of the
N-terminus in NP4 -NO. c, Stereo view of the closed (red lines)
and open (green lines) conformers of NP4, after superimposing
them. In (a) and (b), bonds are open for Asp 30 and filled for
the other residues. Nitrogens are indicated by large open
spheres, carbons by small open spheres, oxygens by shaded
spheres, and hydrogen bonds by dashed lines.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Biol
(2000,
7,
551-554)
copyright 2000.
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Secondary reference #1
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Title
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The crystal structure of nitrophorin 4 at 1.5 a resolution: transport of nitric oxide by a lipocalin-Based heme protein.
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Authors
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J.F.Andersen,
A.Weichsel,
C.A.Balfour,
D.E.Champagne,
W.R.Montfort.
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Ref.
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Structure, 1998,
6,
1315-1327.
[DOI no: ]
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PubMed id
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Figure 6.
Figure 6. Ligand pocket comparison among lipocalins. (a)
Stereoview of the superimposed ligand-binding regions of NP4
(green, with heme), BBP (blue) and INS (red). His61 in BBP and
His131 in INS are close to the NP4 heme iron. (b) Stereo overlay
of BBP, with the biliverdin (blue), and NP4 heme (green).
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The above figure is
reproduced from the cited reference
with permission from Cell Press
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Secondary reference #2
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Title
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Crystal structures of a nitric oxide transport protein from a blood-Sucking insect.
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Authors
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A.Weichsel,
J.F.Andersen,
D.E.Champagne,
F.A.Walker,
W.R.Montfort.
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Ref.
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Nat Struct Biol, 1998,
5,
304-309.
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PubMed id
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