Comparison of E. coli based self-inducible expression systems containing different human heat shock proteins

Area of Science:

• * Biotechnology
• * Molecular Biology
• * Protein Expression Systems

Background:

• * Isopropyl β-D-1-thiogalactopyranoside (IPTG)-inducible promoters are widely used for recombinant protein expression.
• * However, IPTG induction is costly and toxic at industrial scales.
• * Self-Inducible Expression (SILEX) systems offer an alternative using autoinducers like heat shock proteins (HSPs).

Purpose of the Study:

• * To investigate the efficacy of different heat shock proteins (Hsp27, Hsp40, Hsp70) as autoinducers in the SILEX system.
• * To compare SILEX systems with the traditional IPTG-inducible system for protein expression.
• * To evaluate expression levels, bacterial growth, and plasmid/expression stability.

Main Methods:

• * Engineered E. coli strains by co-transforming plasmids for EGFP expression and HSP autoinducers (Hsp27, Hsp40, Hsp70).
• * Quantified EGFP expression using fluorimetry.
• * Assessed bacterial growth curves, plasmid stability, and expression consistency across clones.

Main Results:

• * All SILEX systems successfully self-induced protein expression.
• * The Hsp27-based SILEX system demonstrated higher expression levels than Hsp70/Hsp40 systems, though IPTG remained highest.
• * SILEX systems exhibited greater expression stability over time and among clones compared to IPTG induction, with Hsp27 showing less metabolic burden and variation.

Conclusions:

• * The Hsp27-based SILEX system is a viable autoinducible alternative for recombinant protein production.
• * It offers advantages in terms of metabolic burden, expression consistency, and stability over IPTG-inducible systems.
• * SILEX systems, particularly Hsp27, present a scalable and efficient option for industrial protein expression.