The KT3 epitope tag is commonly engineered onto the N- or C- terminus of a protein of interest so that the tagged protein can be analyzed and visualized using immunochemical methods. KT3 epitope tag can be used to monitor expression of the protein products transfected with cDNA constructs. The recognized KT3 epitope represents the amino acid sequence KPPTPPPEPET derived from the Simian Virus 40 (SV40) large T-antigen.