Tailor-made sugar coated proteins manufactured in novel E. coli system

The prospect of using bacteria to manufacture complex human proteins for use in therapeutic drugs is a step closer thanks to new research published today in Science.

Researchers from Switzerland and the UK report they have engineered the bacterium Escherichia coli to carry a vital piece of cell machinery that adds sugar molecules to newly synthesized proteins by a process known as glycosylation.

The finding opens up the possibility of producing complex human proteins
such as Factor VIII and the hormone erythropoietin, which stimulates the production of red blood cells by stem cells in bone marrow. Both these proteins, which require the addition of sugar molecules to function properly, are currently produced by culturing mammalian cells, which can be a costly and technically difficult process.

The addition of sugars to proteins by glycosylation is crucial in defining their job in the body by helping them fold into a particular three-dimensional shape that determines how they interact with other proteins.

Simple bacterial cells normally do not possess the same type of cellular machinery used for glycosylation in higher organisms like humans. Until now this has restricted the types of human proteins that can be produced in bacteria.

The team of scientists from the Swiss Federal Institute of Technology, Zurich, the London School of Hygiene and Tropical Medicine and Imperial College London have shown that the bacterium Campylobacter jejuni uniquely contains glycosylation machinery similar to the type found in higher organisms. They have developed a technique of transferring this machinery into the E. coli bacterium, which is widely used in the industrial production of proteins.

Professor Anne Dell of Imperial College London said:

“We are only now beginning to understand the vital biological role sugars play in monitoring and guiding the day-to-day lives of the cells in our bodies. This work opens a path for the production of tailor-made glycoproteins in high abundance for applications in research and industry.”

Using new high sensitivity mass spectrometers housed in the Department of Biological Sciences together with facilities in the M-Scan Mass Spectrometry Research and Training Centre, Ascot, the Imperial research team headed by Professor Dell and Professor Howard Morris were able to identify the precise nature of glycosylation in C. jejuni, including the exact position where sugars are attached to proteins.

Colleagues in Zurich were then able to insert the C. jejuni glycosylation machinery into E coli and test whether it worked using mutational analysis.

“We have only begun to scratch the surface in understanding important role sugars play in our body,” said Professor Dell. “Many common diseases including certain types of rheumatoid arthritis and muscular dystrophy have already been linked to disruption of the delicate balance of sugars displayed on the surface of proteins. Deciphering these complex interactions will be significantly aided by the new tool our research has developed.”

Professor Brendan Wren of the London School of Hygiene and Tropical Medicine added:

“C. jejuni is recognised to be the major bacterial cause of gastro-intestinal diseases worldwide and can lead to the development of serious neurological disease. Despite the importance of the organism it is very poorly understood. Apart from its potential in glycoengineering, the newly characterised glycosylation system will also be useful in the development of vaccines to reduce the burden of Campylobacter-related disease”.

The Imperial College London research infrastructure was funded by a JIF grant, which involves partnership between the Wellcome Trust, the Office of Science and Technology and the Higher Education Funding Council for England. Additional support was provided by the Biotechnology and Biological Sciences Research Council (BBSRC) and the Wellcome Trust. Professor Anne Dell currently holds a BBSRC Professorial Fellowship.