With the development of synthetic biology and metabolic engineering, the expression of certain genes in biosynthetic pathways require the expression time and expression level to be controlled. It is necessary to construct a rigorous promoter to keep the gene expression under control. High-copy plasmids are not genetically stable, and low-copy number plasmids are not conducive to high-efficiency expression. Therefore, the strength of the promoter is studied to regulate gene expression.
Synbio Technologies found that the rhamnose promoter positively regulates and induces expression, and the background expression level is much lower than that of other negatively regulated promoters. Among the stringent promoters, the rha promoter expression control range is also much larger.
Synbio Technologies’s lab constructed an E.coli expression vector with an rha promoter. In this test experiment, five Staphylococcus aureus enterotoxin proteins were successfully expressed, including the SED protein that is difficult to express in the PET vector. It can be expressed normally under the regulation of rha promoter.
Lane 2: Flow through
Lane 3: Elution by 50 mM imidazole
Lane 4: Elution by 250 mM imidazole
Lane 5: Elution by 500 mM imidazole
 Ciarán L. Kelly, George M. Taylor, Andrew Hitchcock, Antonio Torres-Méndez, John T. Heap ,A Rhamnose-Inducible System for Precise and Temporal Control of Gene Expression in Cyanobacteria[J]. ACS Synthetic Biology,2018, DOI: 10.1021/acssynbio.7b00435
 QIU Huan-Na, ZHAO Dong-Dong, MAN Shu-Li, BI Chang-Hao, ZHU Xin-Na, ZHANG Xue-Li. Construction of promoters with tight regulation on chromosome of Escherichia coli[J]. Microbiology China, 2018, 45(8): 1693-1704