Improved soluble expression of the gene encoding amylolytic enzyme Amo45 by fusion with the mobile-loop-region of co-chaperonin GroES in Escherichia coli

Abstract

The gene encoding the amylolytic enzyme Amo45, originating from a metagenomic project, was retrieved by a consensus primer-based approach for glycoside hydrolase (GH) family 57 enzymes. Family 57 contains mainly uncharacterized proteins similar to archaeal thermoactive amylopullulanases. For characterization of these family members soluble, active enzymes have to be produced in sufficient amounts. Heterologous expression of amo45 in E.coli resulted in low yields of protein, most of which was found in inclusion bodies. To improve protein production and to increase the amount of soluble protein, two different modifications of the gene were applied. The first was fusion to an N-terminal His-tag sequence which increased the yield of protein, but still resulted in high amounts of inclusion bodies. Co-expression with chaperones enhanced the amount of soluble protein 4-fold. An alternative modification was the attachment of a peptide consisting of the amino acid sequence of the mobile-loop of the co-chaperonin GroES of E.coli. This sequence improved the soluble protein production 5-fold compared to His₆-Amo45 and additional expression of chaperones was unnecessary.

Keywords::

• Metagenome mining
• glycoside hydrolase family 57
• expression in E.coli
• chaperones
• Fusion with the mobile-loop of GroES

Declaration of interest: The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.

The work was supported by the EU FP7 grant 265992 AMYLOMICS.