A LINEAR REGION OF A MONOCLONAL-ANTIBODY CONFORMATIONAL EPITOPE MAPPED ON P185(HER2) ONCOPROTEIN

Analysis of epitopes recognized by therapeutic monoclonal antibodies ( mAb) is critical in clinical applications and in structure/function st udies of target antigen, mAb MGr6 recognizes the extracellular domain of the p185(HER2) oncoprotein and is a promising candidate for cancer immunodiagnosis and immunotherapy. Thus, epitope location and structur e on p185(HER2) need to be investigated. The use of MGr6-selected phag e-displayed peptides for epitope analysis served to dissect the MGr6 e pitope into at least two subregions, mimicked by CHSDC- and (L)P-(L)K( L) phage displayed peptides, respectively. Comparison of amino acid se quences of CHSDC peptides with the p185(HER2) protein sequence and ana lysis of MGr6 reactivity with p185(HER2) deletion mutants identified t he linear subregion CCHEQCAAG of the MGr6 epitope, corresponding to am ino acids 235-243 of the p185(HER2) protein. This continuous subregion is part of a larger conformational epitope, and other ami no acids, i ncluding a proline, a lysine and leucine residues contained in (L)P-(L )K(L) phage-displayed peptides appear to contribute to the formation o f the MGr6 epitope surface.