Co-expression of the small heat shock protein, Lo18, with ß-glucosidase in Escherichia coli improves solubilization and reveals various associations with overproduced heterologous protein, GroEL/ES.

We developed a new system to improve the overproduction of soluble proteins in E. coli based on a plasmid encoding the small heat-shock protein, Lo18, derived from the lactic acid bacterium Oenococcus oeni. The efficiency of this system was compared with that of another system based on production of the E. coli universal chaperone GroEL/ES. A compatible plasmid encoding ß-glucosidase was constructed for the overproduction and aggregation of this enzyme. Co-expression with Lo18 resulted in an increase in soluble ß-glucosidase levels similar to that obtained in the GroEL/ES co-expression system. Lo18 was found preferentially in the insoluble fraction, associated with aggregated enzyme. By contrast, GroEL/ES was more abundant in the soluble fraction.