P43: In vivo nanobioreactors for biosynthesis and biocatalysis

Engineering metabolic pathways into heterologous host cells to produce valuable chemical compounds and biofuels is a major goal of synthetic biology. Factors like alternate metabolic routes and accumulation of toxic reaction intermediates, however, often reduce the efficiency of such engineered pathways. These issues can be addressed by encapsulating the heterologous enzymes and substrates within semi-permeable intracellular compartments. This approach would greatly improve reaction efficiency while also protecting the engineered host cells from potentially toxic reaction intermediates. Several bacteria form protein-based polyhedral microcompartments which sequester functionally related enzymes and regulate their access to substrates and other small metabolites. Such bacterial microcompartments (BMCs) may be engineered into protein-based nano-bioreactors, provided that they can be assembled in a heterologous host, and that heterologous enzymes and substrates can be targeted into the engineered compartments. We report that recombinant expression of BMC shell proteins in E. coli results in the formation of well-defined polyhedral compartments. Further, we show that proteins can be specifically targeted to the compartments in E. coli and that the thus localized proteins are functional. Together our results provide proof-of-concept for the engineering of protein nano-compartments for biocatalysis and biosynthesis.