Influence of N-terminal His-tags on the production of recombinant proteins in the cytoplasm of Bacillus subtilis

The influence of fusion tags to produce recombinant proteins in the cytoplasm of Bacillus subtilis is not well-studied as in E. coli. This study aimed to investigate the influence of His-tags with different codons on the protein production levels of the high expression gene (gfp+) and low expression gene (egfp) in the cytoplasm of B. subtilis cells. We used three different N-terminal His-tags, M-6xHis, MRGS-8xHis and MEA-8xHis, to investigate their effects on the production levels of GFP variants under the control of the Pgrac212 in B. subtilis. The fusions of His-tags with GFP+ caused a reduction compared to the construct without His-tag. When three His-tags fused with egfp, the EGFP production levels were significantly increased up to 3.5-, 12-, and 15-fold. This study suggested that His-tag at the N-terminus could enhance the protein production for the low expression gene and reduce that of the high expression gene in B. subtilis.