IDENTIFICATION OF AN ALLOSTERIC BINDING-SITE ON THE TRANSCRIPTION FACTOR P53 USING A PHAGE-DISPLAYED PEPTIDE LIBRARY

Monoclonal antibody FAb1620 recognizes a conformational epitope on the transcription factor p53 and, upon binding, allosterically inhibits p 53 binding to DNA, A highly diverse (1.5x10(10) members) phage-display ed library of peptides containing 40 random amino acids was used to id entify the PAb1620 binding site on p53, Fanning this library against F Ab1620 resulted in three unique peptides which have statistically sign ificant sequence identities with p53 sufficient to identify the bindin g site as being composed of amino acids 106-113 and 146-156, Based on these results, we propose a mechanism by which PAb1620 can allosterica lly inhibit p53 binding to DNA through an indirect interaction between the antibody binding site and the L1 loop (amino acids 112-124) of p5 3, which is a component of the DNA binding region.