Characterization of the prion protein 3F4 epitope and its use as a molecular tag

These and other observations have led to the commonly accepted notion that the 3F4 epitope consists of the tetra-peptide Met-Lys-His-Met. In this study, we have identified the minimal epitope for 3F4 by studying its binding to synthetic peptides and by analysis of mutated ovine PrP::GFP constructs expressed in cell culture. We have found that the 3F4 epitope consists of a hepta-peptide (Lys-Thr-Asn-Met-Lys-His-Met), which in sheep encompass residues 109-115. We found that Lys 109 is critically important for 3F4 binding, as omission, or substitution of this residue to Ala resulted in no binding. We also demonstrate that the hepta-peptide constituting the minimal 3F4 epitope, can be used as a discrete, moveable high-affinity molecular tag. Thus, the 3F4 antibody can find its use beyond prion research.