The use of TAGZyme for the efficient removal of N-terminal His-tags.

The use of affinity tags and especially histidine tags (His-tags) has become widespread in molecular biology for the efficient purification of recombinant proteins. In some cases, the presence of the affinity tag in the recombinant protein is unwanted or may represent a disadvantage for the projected use of the protein, like in clinical, functional or structural studies. For N-terminal tags, the TAGZyme system represents an ideal approach for fast and accurate tag removal. TAGZyme is based on engineered aminopeptidases. Using human tumor necrosis factor alpha as a model protein, we describe here the steps involved in the removal of a His-tag using TAGZyme. The tag used (UZ-HT15) has been optimized for expression in Escherichia coli and for TAGZyme efficiency. The UZ-HT15 tag and the method can be applied to virtually any protein. A description of the cloning strategy for the design of the genetic construction, two alternative approaches and a simple test to assess the performance of the tag removal process are also included.