Engineering of protein epitopes: a single deletion in a snake toxin generates full binding capacity to a previously unrecognized antibody |
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Authors: | Zinn-Justin Sophie; Pillet Laurence; Ducancel Frdric; Thomas Aline; Smith Jeremy C; Boulain Jean-Claude; Mnez Andr |
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Affiliation: | Dpartement d'lngnierie et d'Etudes des Protines
1Section de Biophysique des Protlnes et des Membranes DBCM, CE-Saclay, 91191 Gif-sur-Yvette cedex, France |
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Abstract: | Structural features associated with the ability of a monoclonalantibody (mAb) to discriminate between protein variants areidentified and engineered. The variants are the curaremimetictoxin from Naja nigricollis and erabutoxin a or b from Laticaudasemifasciata which differ from each other by 16 substitutionsand one insertion. The neutralizing mAb M 1 recognizes with highaffinity a topographical epitope on the surface of toxin , butfails to recognize the erabutoxins although they possess mostof the residues forming the presumed epitope. Examinations ofthe toxin and erabutoxin 3-D structures and molecular dynamicssimulations reveal several differences between the variants.In particular, the region involving the ß-turn 1724is organized differently. Analysis of the differences foundin this region suggests that the insertion (or deletion) atposition 18 of the variant amino add sequences is particularlyimportant in determining the differential cross-reactivity.To test this proposal, residue 18 was deleted in one erabutoxinusing sitedirected mutagenesis, and the biological propertiesof the resulting mutant were examined. We found that full antigenicitywas restored in the previously unrecognized variant. The implicationsof this finding are discussed. |
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Keywords: | antibody antigen binding/ epitope mapping/ sitedirected mutagenesis/ snake toxin/ 3-D structure |
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