ComplexINC tool-kit sets stage to unlock protein complex chemical space

November 09, 2016
MultiBacTAG figure

MultiBacTAG enables incorporation of artificial amino acids into protein complexes for many applications ranging from discovery science to molecular medicine.

Genetic code expansion (GCE) is a powerful method to incorporate artificial amino acids into polypeptide chains to create synthetic proteins with novel functions, with many applications ranging from discovery science to molecular medicine.

Until recently, this method has been mostly confined to small individual proteins representing a limited repertoire of cellular activity. Biological function in humans, however, is typically catalyzed by large protein machines, often comprising ten or more individual protein subunits. An international team of scientists from University of Bristol, EMBL and the Karlsruhe Institute of Technology have now developed MultiBacTAG, a powerful system to enable genetic code expansion in complex multiprotein machines.

“We used ComplexINC’s leading MultiBac technology for protein complex production, as a starting point, and outfitted this system with the molecular gadgets required for genetic code expansion in eukaryotes”  explains ComplexINC Coordinator Imre Berger. MultiBac relies on a recombinant baculovirus engineered by the Berger group for high-quality protein complex production in insect cell cultures infected by the virus. The scientists incorporated a particular tRNA and its cognate orthogonal amino-acid synthetase directly into the backbone of the MultiBac virus. This tRNA/synthetase pair recognizes a specific site - usually a signal to arrest protein synthesis - in newly produced polypeptides, and incorporates unnatural amino acids exactly at these sites in the complexes produced with the MultiBac technology.

“It is great to see how our MultiBac system keeps on growing,” says Daniel Fitzgerald, CEO of Geneva Biotech, the ComplexINC start-up which commercializes intelligent biotechnologies including MultiBac. “It has developed into a kind of trademark scientists in many institutions in academia and industry now rely on to accelerate their R&D programs.”

Current MultiBacTAG applications include artificial amino acid cross-linking to map interactions in protein complexes, fluorescence labelling of specific targets to measure structure and dynamics in proteins and glycol-engineering proteins compatible with human tissue studies. The scientists anticipate that the platform will also provide exciting possibilities to custom-design proteins for therapeutic biotechnology and pharmaceutical applications. For example, in their paper the team used MultiBacTAG to engineer Herceptin – an antibody that associates with cancer cells – to recognise breast cancer cells in human tissue.