Novel Propeptides for Enhanced Secretion from Lactococcus Lactis

Lactic acid bacteria (LAB) are a "generally regarded as safe" microorganisms which are traditionally used in food fermentation and as chassis for heterologous protein production. In recent years, they have also emerged as delivery tools for protein therapeutics. However, these applications are heavily depended on the secretion efficiencies and capabilities of LAB. Secretion of proteins will not only simplify the purification process but also oftentimes increase total protein production. Besides utilizing an efficient signal peptide, importance of a suitable propeptide for soluble, secreted heterologous protein production was also emphasized in previous studies (1, 2). To expand the propeptide library for protein secretion in LAB, we identified three propeptide candidates from in silico mining of LAB genomes. Here, we will examine and compare these propeptides for enhanced protein secretion in Lactococcus lactis. These will also be compared to a known and highly productive propeptide "LEISSTCDA" (1). Secretion efficiencies and yields of these propeptides will be characterized and examined for a variety of model proteins. From the success of these propeptides to enhance secretion, we predict that this collection of propeptides will be invaluable to future heterologous protein secretion optimisation in LAB. 

(1) Le Loir Y, Gruss A, Ehrlich SD, Langella P. A Nine-Residue Synthetic Propeptide Enhances Secretion Efficiency of Heterologous Proteins inLactococcus lactis. Journal of Bacteriology. 1998;180(7):1895-1903.

(2) Le Loir Y, Nouaille S, Commissaire J, Brétigny L, Gruss A, Langella P. Signal Peptide and Propeptide Optimization for Heterologous Protein Secretion in Lactococcus lactis. Applied and Environmental Microbiology. 2001;67(9):4119-4127