PROTEIN SEPARATION: Taking a genetic approach

Georges Belfort, professor of chemical engineering at Rensselaer Polytechnic Institute and a world-renowned authority on separation science, took a genetic approach to solving a critical problem in affinity fusion separation of proteins.

Affinity fusion separation has been used for some time in laboratories, but it has not successfully been scaled up for the commercial production of desirable proteins, such as insulin. The goal is to fuse the desired protein to a binding protein, which holds it while everything else is washed through. The target protein must then be cut from the binder. Until now, this has generally been done by adding a protease, an enzyme capable of cutting proteins.

The addition of protease, however, creates major problems. It must be completely removed, which involves additional costly steps, and there is danger of contamination because an enzyme that cuts up proteins can’t be safely included in a drug.

In work reported in Nature Biotechnology, the Belfort team used genetic methods to insert an intein, a naturally occurring sequence, into the binding protein. The intein is sensitive to acid concentration and temperature. By changing physical conditions in the mixture, the researchers can cause the intein to break on cue and release the desired protein. Inserting the intein thereby eliminates the need for a protease.

To create a workable system, graduate student David Wood and other team members used genetic engineering and a random-mutation strategy to create a very efficient mini-intein. Several major biotechnology firms are considering commercializing the process.

Belfort collaborated on the project with his wife, Marlene Belfort, director of the Division of Genetic Disorders at the Wadsworth Center, New York State Department of Health, and professor of biomedical sciences at the State University of New York School of Public Health.

CONTACT: Theresa Bourgeois, (518) 276-2840, bourgt@rpi.edu

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