The recognized AU1 sequence represents the amino acid sequence DTYRYI, derived from the major capsid protein of bovine papillomavirus-1 (BPV-1). AU1 is a commonly used epitope tag engineered onto the N- or C- terminus of a protein of interest so that the tagged protein can be analyzed and visualized by immunochemical methods. This antibody recognizes the AU1-tag fused to the carboxyl terminus of targeted proteins.