Bacterial Protein Production System



The invention is a host/vector system uniquely suited for the expression of membrane proteins that takes advantage of an unusual attribute of the bacterium Rhodospirillum rubrum. R. rubrum forms an extensive intracytoplasmic membrane (ICM), which is non-essential for growth, in response to membrane protein synthesis. The host in this system is a mutant R. rubrum strain that does not synthesize its own, major membrane proteins and thus does not natively form ICM; however, the strain retains the ability to make ICM in response to the production of foreign membrane proteins. Thus, because the strain can produce ICM in the absence of its own membrane proteins, it can incorporate foreign and over-expressed membrane proteins into this “extra” membrane without disrupting normal cellular function. In addition, gene expression in this system is regulated by oxygen, allowing expression to be controlled by a simple means that does not require potentially toxic or costly chemical inducers. The result is a high-yield expression system that can be used to produce a large number of active membrane proteins in a native conformation.

Membrane proteins account for between 30-50% of the most promising pharmaceutical targets. However human membrane proteins have not been studied in great detail because it is difficult to synthesize them in large quantities. Researchers currently use the bacterium E. coli to produce minute amounts of heterologous (non-bacterial) membrane proteins, but this production often kills the host cell or yields inactive, improperly folded proteins.


  • Protein Expression Capabilities – Expression of several foreign membrane proteins has been demonstrated in this system which can be used to express and purify multiple types of membrane proteins, including human membrane proteins
  • High Yield – Potential for efficient, large-scale production for non-infectious vaccines, protein therapeutics, enzyme therapies, and basic research
  • Simple Purification – ICM is readily separated from other cellular material, easing membrane protein purification
  • Simple, Low Cost Promoter – Expression vector contains a promoter induced by reduced oxygen concentration, a simple, low-cost stimulus applicable to both laboratory and production scales
  • Safety – Host is easy to work with – rubrum is non-pathogenic to humans and grows on simple media

Intellectual Property

U.S. Patent 6,680,179
U.S. Patent 6,951,741
U.S. Patent 8,481,287

This technology is seeking partners for development of the final product. Several academic and pharmaceutical based laboratories have tested or are currently testing the kit for efficacy.  It is available licensing under either exclusive or non-exclusive terms.


Butzin, N.C; Owen, H.A.; and M.L.P. Collins. 2010. A new system for heterologous expression of membrane proteins: Rhodospirillum rubrum. Protein Expression and Purification, 70: 88-94.

Inventor (s)

Dr. M.L.P. Collins is a Professor Emerita in the Department of Biological Science at UWM specializing in Microbial physiology. She earned a Ph.D. in Microbiology from Rutgers University and was a Postdoctoral Fellow at NYU School of Medicine.

For further information please contact:
Jessica Silvaggi, Ph.D.
Director of Technology Commercialization
UWM Research Foundation
1440 East North Avenue
Milwaukee, WI 53202
Tel: 414-906-4654
Please reference: OTT ID. 1006