Anti-V5 is optimally suited for monitoring expression of V5-tagged fusion proteins. The V5 epitope tag is derived from a small epitope (Pk) present on the P and V proteins of the paramyxovirus of simian virus 5 (SV5). The V5 tag is usually used with all 14 amino acids (GKPIPNPLLGLDST), although it has also been used with a shorter 9 amino acid sequence (IPNPLLGLD). This antibody has been tested by ELISA and western blotting against both the immunizing peptide and V5 containing recombinant proteins.