The Escherichia coli (E. coli) expression system has been widely used to produce recombinant proteins. However, in some heterologous expressions, there are still difficulties in large-scale production. The use of fusion partners is one of the strategies for improving the expression levels of proteins in E. coli host. Here, we demonstrate a novel fusion element, the NT11-tag, which enhances protein expression. The NT11-tag was derived from the first 11 amino acid residues within the N-terminal N-half domain of a duplicated carbonic anhydrase (dCA) from Dunaliella species. Previously, we have found that the tag improves expression of the C-half domain of dCA when linked to its N-terminus. To verify its use as a protein production enhancer tag, two kinds of CAs derived from Hahella chejuensis (Hc-CA) and Thermovibrio ammonifican (Ta-CA) and the yellow fluorescent protein (YFP) were used as model proteins to measure their increased expression upon fusion with the NT11-tag. The NT11-tag amplified protein expression in E. coli by 6.9- and 7.6-fold for Ta-CA and YFP, respectively. Moreover, the tag also enhanced the soluble expression of Hc-CA, Ta-CA, and YFP by 1.7-, 5.0-, and 3.2-fold, respectively. Furthermore, protein yield was increased without inhibiting protein function. These results indicate that the use of the NT11-tag is a promising method for improving protein production in E. coli.
Keywords: CO2 hydration; Esterase activity; Fusion partner; Solubility enhancement tag.