Exploring epitopes of antibodies toward the human tryptophanyl-tRNA synthetase

There is a need to characterize the epitopes of affinity reagents to develop high quality affinity reagents for research, diagnostics and therapy. Here, we describe the analysis of epitopes of antibodies generated toward human tryptophanyl-tRNA synthetase (WARS) using both combinatorial bacterial display and suspension bead array. The bacterial display revealed that the polyclonal antibody binds to three separate epitopes and peptide scanning using 15-mers revealed binding to a 13 amino acid consensus sequence (ELINRIERATGQR). A mouse monoclonal antibody was generated and the mapping approach revealed binding toward a slightly shifted position of the same epitope. Structural analysis showed that the antibodies bind to alpha-helical regions on the surface of the target protein. An alanine-scanning experiment showed binding to four specific residues. The implications for the systematic analysis of antibody epitopes on the basis of these results are discussed.