Harnessing the Profinity eXact™ System for Expression and Purification of Heterologous Proteins in E. coli.

Highly purified recombinant proteins in large quantities are valuable material for biochemical and structural studies. To achieve this goal, versatile tools were developed to increase the expression of the recombinant proteins and to facilitate the purification process. Fusion tags are commonly used for enhancing expression and solubility and some can be used in the purification process. However, these tags may need to be removed by treatment with specific proteases in order to obtain the tag-free protein. The Profinity eXact™ system provides an alternative system for a fusion tag, enhancing expression and purification in one-step. Here we describe a set of new vectors in which the Profinity eXact™ tag, in addition to a 6× His-tag, with or without additional expression-enhancing sequences, could be used in the Profinity eXact™ system. We show that the solubility enhancing tags (Trx, GST, GB1) increase the yield of the purified tested protein compared to the vector containing only a His-tag upstream of the Profinity eXact™ fusion tag.