title: Potential of peptides selected from random phage-displayed libraries to mimic conformational epitopes: a study on scorpion toxin Cn2 and the neutralizing monoclonal antibody BCF2.
abstract: Many conformational epitopes cannot be mapped by the use of a phage display approach due to the lack of amino acid similarity with the selected peptides. Exploring the potential of the method, we selected mimotopes of the discontinuous, highly conformational epitope of scorpion neurotoxin Cn2, whose 3D structure is known, using its generic neutralizing monoclonal antibody BCF2. With an exhaustive selection procedure, we isolated from a 12-mer phage library a large collection of mimotopes that reproduce the antigenic and immunogenic specificity of the Cn2-epitope. The selected peptides presented three sequence motifs, the most abundant of which, RD(N)XXGF, appeared in 15 different sequence contexts displayed by 97 out of 206 clones. In the most reactive mimotope, displayed by 24 (25%) clones, the motif was flanked by two Cys residues allowing the adoption of a cyclic conformation. Motifs QL(H,M)L(M) and (S/T)WHLP were selected with less efficiency. Comparison of the motifs with the primary and three-dimensional structure of Cn2 as well as with a model of the Cn2-BCF2(Fv) complex suggests that RD(N)XXGF, which does not share sequence similarity with the epitope, mimics its central structural element, turn 7-11, by using an alternative amino acid combination nevertheless keeping the nature of its interactions with BCF2. The QL(H,M)L(M) is assumed to mimic the hydrophobic part of the epitope. The principles of the conformational mimicry by phage-displayed peptides are discussed.
authors.affiliation: Laboratory of Molecular Genetics, Department of Biotechnology, Instituto de Investigaciones Biomédicas, Universidad Nacional Autnóma de México, Ciudad Universitaria, 04510 México D.F., México.
authors.forename: Tatiana G
authors.initials: TG
authors.lastname: Gazarian
authors.forename: Barbara
authors.initials: B
authors.lastname: Selisko
authors.forename: Georgina B
authors.initials: GB
authors.lastname: Gurrola
authors.forename: Ricardo
authors.initials: R
authors.lastname: Hernández
authors.forename: Lourival D
authors.initials: LD
authors.lastname: Possani
authors.forename: Karlen G
authors.initials: KG
authors.lastname: Gazarian
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000276:immunology; D000939:Epitopes / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008958:Models, Molecular; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D019151:Peptide Library; D010455:Peptides / Q000302:isolation & purification*; D011487:Protein Conformation; D012604:Scorpion Venoms / Q000737:chemistry* / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D000939:Epitopes; D019151:Peptide Library; D010455:Peptides; D012604:Scorpion Venoms