The CL7 Affinity Tag System

The Problem


The process of protein purification often becomes a major bottleneck in research. Tag-based purification methods such as the His-tag system are widely accepted, but they have not been significantly improved upon since their release and adoption. Traditional protocols can take several days to run which results in a loss of time and end product.

The CL7 Tag System

TriAltus’s CL7 tag system is based on the ultra-high-affinity interaction between a variant of the Colicin E7 DNAse (CL7) and its inhibitor, Immunity protein 7 (Im7). The Im7 inhibitor is covalently crosslinked to agarose beads, while the CL7 domain is tagged to the target protein. CL7-tagged vectors are customized to insert the tag at the C or N-terminal of the protein and allow for the inclusion of other tag domains and cleavage sites by a variety of proteases. Once the protease has cleaved off the protein, the CL7 tag can be removed from the column and the Im7 resin reused.

Efficient, ultra-high-affinity chromatography in a one-step purification of complex proteins (Figure 1B).


Our CL7/Im7 system continues to be validated by research groups around the world as they apply our purification framework to their area of study.

Our novel method has been tested and verified for activity in difficult-to-purify proteins such as those that are DNA/RNA binding, eukaryotic, membrane, toxic, or multi-subunit. 

Read more below about how we and other groups have adopted the CL7 tag purification system in numerous studies.


TriAltus Bioscience holds the exclusive, worldwide license to the CL7 protein purification technology platform. It was licensed from the University of Alabama at Birmingham (UAB) in Birmingham, Alabama, USA.  An international patent filing has been made with protection being sought in the United States, Europe, and other major markets. The CL7 purification technology is available for research use. For commercial use or resale, contact us at to discuss commercial licensing. 


Looking for more resources? 

Reference our protocol for more information. For further inquiries, please contact us directly at


Want to test it yourself? 

We offer a limited free sample program for researchers who would like to validate our system in their own labs. Please contact us directly at to discuss your needs and how CL7/Im7 can be integrated into your research.