IPTG-independent autoinduction of extracellular matrix proteins using recombinant E. coli as the expression host

Abstract

At present, isopropyl β-D-thiogalactopyranoside (IPTG) is the universal inducer for expressing recombinant proteins under the lac operator/repressor system. In this study, we propose an autoinduction (IPTG-independent) system for recombinant proteins using E. coli as the expression host. We applied this bacterial host for autoinduction to the expression of recombinant proteins, including green fluorescence protein (GFP) and an artificial extracellular matrix protein (aECM-CS5-ELF). The host harbors a mutant Ala294Gly/Thr251Gly phenylalanyl-tRNA synthetase (PheRS**) with an enlarged binding pocket that is expressed under the control of the T7 promoter. Using this system, we demonstrate marked overexpression of the biosynthesized GFP and aECM-CS5-ELF from a 1-L culture containing glucose (5 g/L) and galactose (20 g/L) as the carbon sources, with GFP and aECM-CS5-ELF yields 2.3- and 8.1-fold higher, respectively, than that from an IPTG-induced culture. This unique trial is intended to stimulate novel overexpression strategies based on autoinduction. We chose an autoinduction (IPTG-independent) system for overexpression of recombinant proteins using E. coli as the expression host. In autoinduction, glucose and lactose are used as main carbon sources for cell growth. When the glucose is almost completely consumed as the first growth of E. coli., the carbon source turns to lactose, accompanied by regioselective chemical transformation of lactose to allolactose, which acts as the trigger for activation of transcription by releasing the repressor. Using this system, we achieved marked overexpression of the biosynthesized GFP and aECM-CS5-ELF.