(820b) Controlling Transcriptional Regulation of a Secretion System for Increased Recovery of Folded Heterologous Proteins From the Culture Media

Secretion of heterologous proteins in a bacterial culture allows for simplified purification, compared to intracellular expression. However, there is often accumulation of the protein targeted for secretion in the cytosol, resulting in lower yields of protein in the culture media. Previous studies indicated that low native gene expression of a type III secretion system (T3SS) may be limiting titers of secreted protein in this system. We report the engineered expression of a transcription factor, HilA, that transcriptionally regulates a native T3SS from Salmonella enterica for high titer yields of diverse heterologous proteins. HilA is a transcriptional activator that has direct and downstream control of the expression of over five transcriptional units that are associated with the T3SS. We characterized the changes in gene expression and protein secretion as a result of the tuned expression of HilA and were able to achieve greater than a 10-fold increase in secreted protein titer. These data demonstrate the use of transcriptional control to achieve a desired performance from a native genetic device.