HELICAL EPITOPES DETERMINED BY LOW-STRINGENCY ANTIBODY SCREENING OF ACOMBINATORIAL PEPTIDE LIBRARY

Combinatorial phage display peptide libraries are routinely used to ma p epitopes of specific monoclonal antibodies. In this study we illustr ate that these libraries can be used in tile analysis of protein struc ture, By screening libraries at low stringency, a collection of phages can be obtained, These are characterized by the fact that they are re cognized by a given monoclonal antibody yet with various affinities. C omparing the random peptides of these phages indicates the common esse ntial residues necessary for antibody recognition. Aligning the insert s based on the detected homology has revealed structural motifs that c orrespond to secondary protein structures, The envelope protein of HIV -1 has been studied using this approach, A combinatorial phage display Library containing a 20 mer random peptide ill protein III of the fil amentous phage fd-tet has been used to analyze two different monoclona l antibodies directed against gp120. Our results provide experimental evidence that indicate that the C1 domain of gp120 contains an alpha h elix.