The epitope recognized by a monoclonal antibody in the myelin-associated protein CNP

The epitope recognized by a monoclonal antibody (MAb-46-1) directed against the myelin-associated protein CNP (2',3'-cyclic nucleotide 3'-phosphodiesterase; EC 3.1.4.37) from several species was characterized. MAb-46-1 can be employed for immunoprecipitation, immunostaining in Western blots and in immunohistochemistry. Short peptides derived from the human CNP1 peptide sequence were synthesized and used in enzyme linked immunosorbent assays to test the reactivity of MAb-46-1. Coarse screening experiments enabled us to localize the epitope recognized by MAb-46-1 to the amino acid residues 9 to 19 close to the N-terminus. Further investigations using shorter peptides comprising this part of the protein allowed us to identify a 9 amino acid residue long peptide (amino acids 11 to 19: ELQFPFLQD) which represents the minimal epitope recognized by MAb-46-1, probably through a 3-dimensional structure and less likely a straight linear peptide. The epitope seems to be stabilized also by the attached amino acids 7 to 10 (KDKP). The peptide sequence 9-19 is conserved in all CNP sequences described so far. Thus, MAb-46-1 might be of general usefulness for further studies of the not yet identified function of the myelin-associated protein CNP.