X-press Tag Peptide is a tag peptide used for protein purification. X-press Tag is also an N-terminal leader peptide; this N-terminal peptide contains a polyhistidine sequence, the Xpress epitope (part of bacteriophage T7 gene 10 protein) and an enterokinase cleavage site. Anti-Xpress antibodies recognize the Xpress epitope sequence found in this leader peptide.