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. Although not tested, this antibody is likely functional for immunoprecipitation and immunocytochemistry.