SELECTION OF PHAGE-DISPLAYED PEPTIDES MIMICKING AN EXTRACELLULAR EPITOPE OF HUMAN MDR1-P-GLYCOPROTEIN

To study the structural conformation of the MM4.17 monoclonal antibody (mAb) epitope, twenty-six mAb MM4.17-specific phage clones were affin ity-isolated and their inserts characterized for aminoacid composition and homology with MDR1 gene product (MDR1-P-glycoprotein). The result ing sequence alignment shows that a unique consensus sequence, which c orresponds to the previously mapped TRIDDPET linear peptide identified through synthetic peptide scanning, could not be identified. However, similarities between the inserts of positive phage clones and P-glyco protein primary structure, consisting in two or three aminoacid-long s equences, were observed. An analysis of the over-represented aminoacid residues in the inserts of positive clones, and their comparison with the sequence of the antigen was also performed. The two different pro cedures led to the identification of four regions in which these simil arities are clustered, indicating that four different antigen regions, one of which includes the TRIDDPET linear aminoacid sequence, might p articipate in forming the structure of monoclonal antibody MM4.17 epit ope.