MultiBacTAG: Unlocking Protein Complex Chemical Space
28 October 2016
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 MultiBac, our leading technology for protein complex production, as a starting point, and outfitted this system with the molecular tool-kit required for genetic code expansion in eukaryotes” explains Imre Berger from the School of Biochemistry, University of Bristol. 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.
Current MultiBacTAG’s 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.
MultiBacTAG paper in Nature Methods www.nature.com/nmeth/journal/vaop/ncurrent/full/nmeth.4032.html
Edward Lemke at EMBL http://www.embl.de/research/units/scb/lemke/
Stefan Braese at Karlsruhe Institute of Technology, Germany https://www.ioc.kit.edu/braese/english/24.php
Imre Berger, at University of Bristol www.bris.ac.uk/biochemistry/people/imre-berger/index.html
MultiBac platform at the Berger lab, University of Bristol www.bristol.ac.uk/biochemistry/research/technologies/multiexpression/multibac/