BTag: a novel six-residue epitope tag for surveillance and purification of recombinant proteins.

Epitope tagging (Eta) is becoming an increasingly useful technique in molecular biology and biotechnology for the detection, characterisation and purification of recombinant proteins (re-proteins). Here we describe a novel Eta system composed of two different monoclonal antibodies (mAb; D11 and F10) and a 6-amino-acid Eta (Gln-Tyr-Pro-Ala-Leu-Thr or QYPALT). This Eta was derived from a highly conserved region of the major core protein, VP7, of bluetongue (BT) viruses, hence the name BTag. BTag is unique among current tagging systems in its lack of charge and the fact the tag sequence can be placed and detected in any region of a re-protein. Other useful features of BTag include its small size and its recognition by two different mAb. Using the BTag system, more than 30 re-proteins have been produced from a variety of host organisms, and the antigenicity of the tag sequence was maintained in all of the proteins tested to date. Our result demonstrated that BTag could be superior to other existing Eta systems for certain applications.