A neurofilament polypeptide and the glial fibrillary acidic protein share common epitopes in the variable region

A polyclonal antibody against the high molecular weight neurofilament polypeptide (NF-H) obtained from cytoskeletal extracts of bovine spinal cord reacted with NF-H, with the middle molecular weight neurofilament polypeptide (NF-M) and with a M(r) 51,000 polypeptide, but not with the low molecular weight neurofilament polypeptide (NF-L). The M(r) 51,000 polypeptide corresponded to the glial fibrillary acidic protein (GFAP), which forms the intermediate filaments of astrocytes. The polyclonal antibody affinity-purified with GFAP, reacted with both purified GFAP and NF-H. Digestion of NF-H with alpha-chymotrypsin was used to determine the recognition site of the affinity-purified antibodies. Only fragments of the tail domain of NF-H reacted with the antibody. We propose that common epitopes exist between the variable C-terminal domains of NF-H and GFAP.