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PDBsum entry 1i9i
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Immune system
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PDB id
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1i9i
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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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Structural insights into steroid hormone binding: the crystal structure of a recombinant anti-Testosterone FAB fragment in free and testosterone-Bound forms.
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Authors
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J.Valjakka,
K.Takkinenz,
T.Teerinen,
H.Söderlund,
J.Rouvinen.
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Ref.
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J Biol Chem, 2002,
277,
4183-4190.
[DOI no: ]
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PubMed id
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Abstract
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The monoclonal anti-testosterone antibody (3-C(4)F(5)) has a relatively high
affinity (3 x 10(8) m(-1)) with an overall good specificity profile. However,
the earlier characterized binding properties have shown that both the affinity
and specificity of this antibody must be improved if it is intended for use in
clinical immunoassays. In this paper, the crystal structures of the recombinant
anti-testosterone (3-C(4)F(5)) Fab fragment have been determined in the
testosterone-bound and free form at resolutions of 2.60 and 2.72 A,
respectively. The high affinity binding of the (3-C(4)F(5)) Fab is mainly
determined by shape complementarity between the protein and testosterone. Only
one direct hydrogen bond is formed between the hydroxyl group of the
testosterone D-ring and the main-chain oxygen of Gly100(J)H. The testosterone is
deeply bound in a hydrophobic pocket, and the close shape complementarity is
mainly formed by the third complementarity-determining regions (CDR) of the
heavy and light chain. Comparison of the bound structure with the free structure
indicates conformational changes in the protein upon testosterone binding. The
conformational changes of the side chains of two residues Glu95H and Tyr99H in
the CDR-H3 are particularly essential for the binding. Interesting similarities
in the binding of different steroids were also observed upon comparison of the
available structures of anti-steroid antibodies.
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Figure 8.
Fig. 8. Comparison of the binding mechanism of the
anti-testosterone Fab (top), anti-progesterone Fab DB3 (5)
(middle), and anti-digoxin Fab (8) (bottom). The free structures
are shown in pink and steroid complexes in black. Stereopairs
were prepared with the Molscript program (41).
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Figure 10.
Fig. 10. Schematic diagrams of the steroid binding sites.
A, the anti-testosterone Fab; B, the anti-progesterone Fab (5);
C, the anti-digoxin Fab 26-10 (8), and D, the Fv4155 (10)
fragments.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2002,
277,
4183-4190)
copyright 2002.
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Secondary reference #1
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Title
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X-Ray studies of recombinant anti-Testosterone FAB fragments: the use of peg 3350 in crystallization.
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Authors
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J.Valjakka,
A.Hemminki,
T.Teerinen,
K.Takkinen,
J.Rouvinen.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 2000,
56,
218-221.
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PubMed id
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