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PDBsum entry 6mxr
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Immune system
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PDB id
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6mxr
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References listed in PDB file
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Key reference
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Title
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Binding symmetry and surface flexibility mediate antibody self-Association.
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Authors
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J.D.Schrag,
M.Ã.ˆ.Picard,
F.Gaudreault,
L.P.Gagnon,
J.Baardsnes,
M.S.Manenda,
J.Sheff,
C.Deprez,
C.Baptista,
H.Hogues,
J.F.Kelly,
E.O.Purisima,
R.Shi,
T.Sulea.
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Ref.
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MAbs, 2019,
11,
1300-1318.
[DOI no: ]
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PubMed id
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Abstract
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Solution stability is an important factor in the optimization of engineered
biotherapeutic candidates such as monoclonal antibodies because of its possible
effects on manufacturability, pharmacology, efficacy and safety. A detailed
atomic understanding of the mechanisms governing self-association of natively
folded protein monomers is required to devise predictive tools to guide
screening and re-engineering along the drug development pipeline. We
investigated pairs of affinity-matured full-size antibodies and observed
drastically different propensities to aggregate from variants differing by a
single amino-acid. Biophysical testing showed that antigen-binding fragments
(Fabs) from the aggregating antibodies also reversibly associated with
equilibrium dissociation constants in the low-micromolar range. Crystal
structures (PDB accession codes 6MXR, 6MXS, 6MY4, 6MY5) and bottom-up
hydrogen-exchange mass spectrometry revealed that Fab self-association occurs in
a symmetric mode that involves the antigen complementarity-determining regions.
Subtle local conformational changes incurred upon point mutation of monomeric
variants foster formation of complementary polar interactions and hydrophobic
contacts to generate a dimeric Fab interface. Testing of popular in
silico tools generally indicated low reliabilities for predicting the
aggregation propensities observed. A structure-aggregation data set is provided
here in order to stimulate further improvements of in silico tools for
prediction of native aggregation. Incorporation of intermolecular docking,
conformational flexibility, and short-range packing interactions may all be
necessary features of the ideal algorithm.
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