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PDBsum entry 4glr
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Immune system
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PDB id
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4glr
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References listed in PDB file
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Key reference
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Title
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An ultra-Specific avian antibody to phosphorylated tau protein reveals a unique mechanism for phosphoepitope recognition.
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Authors
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H.H.Shih,
C.Tu,
W.Cao,
A.Klein,
R.Ramsey,
B.J.Fennell,
M.Lambert,
D.Ní shúilleabháin,
B.Autin,
E.Kouranova,
S.Laxmanan,
S.Braithwaite,
L.Wu,
M.Ait-Zahra,
A.J.Milici,
J.A.Dumin,
E.R.Lavallie,
M.Arai,
C.Corcoran,
J.E.Paulsen,
D.Gill,
O.Cunningham,
J.Bard,
L.Mosyak,
W.J.Finlay.
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Ref.
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J Biol Chem, 2012,
287,
44425-44434.
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PubMed id
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Abstract
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Highly specific antibodies to phosphoepitopes are valuable tools to study
phosphorylation in disease states, but their discovery is largely empirical, and
the molecular mechanisms mediating phosphospecific binding are poorly
understood. Here, we report the generation and characterization of extremely
specific recombinant chicken antibodies to three phosphoepitopes on the
Alzheimer disease-associated protein tau. Each antibody shows full specificity
for a single phosphopeptide. The chimeric IgG pT231/pS235_1 exhibits a K(D) of
0.35 nm in 1:1 binding to its cognate phosphopeptide. This IgG is murine
ortholog-cross-reactive, specifically recognizing the pathological form of tau
in brain samples from Alzheimer patients and a mouse model of tauopathy. To
better understand the underlying binding mechanisms allowing such remarkable
specificity, we determined the structure of pT231/pS235_1 Fab in complex with
its cognate phosphopeptide at 1.9 Å resolution. The Fab fragment exhibits
novel complementarity determining region (CDR) structures with a
"bowl-like" conformation in CDR-H2 that tightly and specifically
interacts with the phospho-Thr-231 phosphate group, as well as a long,
disulfide-constrained CDR-H3 that mediates peptide recognition. This binding
mechanism differs distinctly from either peptide- or hapten-specific antibodies
described to date. Surface plasmon resonance analyses showed that pT231/pS235_1
binds a truly compound epitope, as neither phosphorylated Ser-235 nor free
peptide shows any measurable binding affinity.
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