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PDBsum entry 1q0x
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Immune system
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PDB id
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1q0x
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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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Anchoring a cationic ligand: the structure of the FAB fragment of the anti-Morphine antibody 9b1 and its complex with morphine.
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Authors
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E.Pozharski,
M.A.Wilson,
A.Hewagama,
A.B.Shanafelt,
G.Petsko,
D.Ringe.
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Ref.
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J Mol Biol, 2004,
337,
691-697.
[DOI no: ]
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PubMed id
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Abstract
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The crystal structures of an anti-morphine antibody 9B1 (to 1.6A resolution) and
its complex with morphine (to 2.0 A resolution) are reported. The
morphine-binding site is described as a shallow depression on the protein
surface, an unusual topology for a high-affinity ( Ka approximately 10(9) M(-1))
antibody against a small antigen. The polar part of the ligand is exposed to
solvent, and the cationic nitrogen atom of the morphine molecule is anchored at
the bottom of the binding site by a salt-bridge to a glutamate side-chain.
Additional affinity is provided by a double cation-pi interaction with two
tryptophan residues. Comparison of the morphine complex with the structure of
the free Fab shows that a domain closure occurs upon binding of the ligand.
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Figure 2.
Figure 2. Stereo view of the morphine-binding site. Shown
are nine residues forming a contact surface for the ligand.
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Figure 3.
Figure 3. A drawing of the binding site. A, Cation-p
interaction of the morphine amine and the aromatic side-chains
of TrpL91 and TrpH95. B, The salt-bridge between the morphine
nitrogen atom and the carboxylate group of GluH50. C, Hydrogen
bonding network around the GluH50 side-chain. D, The water
molecule in the hapten-binding pocket.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2004,
337,
691-697)
copyright 2004.
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