Expression and purification of biologically active recombinant rabbit monocyte chemoattractant protein1 in Escherichia coli

Maximizing the recovery of the native p28 bacterial peptide with improved activity and maintained solubility and stability in Escherichia coli BL21 (DE3)

p28 is a natural bacterial product, which recently has attracted much attention as an efficient cell penetrating peptide (CPP) and a promising anticancer agent. Considering the interesting biological qualities of p28, maximizing its expression appears to be a prominent priority. The optimization of such bioprocesses might be facilitated by utilizing statistical approaches such as Design of Experiment (DoE). In this study, we aimed to maximize the expression of "biologically active" p28 in Escherichia coli BL21 (DE3) host by harnessing statistical tools and experimental methods. Using Minitab, Plackett-Burman and Box-Behnken Response Surface Methodology (RSM) designs were generated to optimize the conditions for the expression of p28. Each condition was experimentally investigated by assessing the biological activity of the purified p28 in the MCF-7 breast cancer cell line. Seven independent variables were investigated, and three of them including ethanol concentration, OD₆₀₀ of the culture at the time of induction, and the post-induction temperature were demonstrated to significantly affect the p28 expression in E. coli. The cytotoxicity, penetration efficiency, and total process time were measured as dependent variables. The optimized expression conditions were validated experimentally, and the final products were investigated in terms of expression yield, solubility, and stability in vitro. Following the optimization, an 8-fold increase of the concentration of p28 expression was observed. In this study, we suggest an optimized combination of effective factors to produce soluble p28 in the E. coli host, a protocol that results in the production of a significantly high amount of the biologically active peptide with retained solubility and stability.

Targeting of cholera toxin A (ctxA) gene by zinc finger nuclease: pitfalls of using gene editing tools in prokaryotes

Background and purpose:

The study was launched to use zinc finger nuclease (ZFN) technology to disrupt the cholera toxin gene (ctxA) for inhibiting CT toxin production in Vibrio cholera (V. cholera).

Experimental approach:

An engineered ZFN was designed to target the catalytic site of the ctxA gene. The coding sequence of ZFN was cloned to pKD46, pTZ57R T/A vector, and E2-crimson plasmid and transformed to Escherichia coli (E. coli) Top10 and V. cholera. The efficiency of ZFN was evaluated by colony counting.

Findings/Results:

No expression was observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blotting in transformed E. coli. The ctxA gene sequencing did not show any mutation. Polymerase chain reaction on pKD46-ZFN plasmid had negative results. Transformation of E. coli Top10 with T/A vectors containing whole ZFN sequence led to 7 colonies all of which contained bacteria with self-ligated vector. Transformation with left array ZFN led to 24 colonies of which 6 contained bacteria with self-ligated vector and 18 of them contained bacteria with vector/left array. Transformation of V. cholera with E2-crimson vectors containing whole ZFN did not produce any colonies. Transformation with left array vectors led to 17 colonies containing bacteria with vector/left array. Left array protein band was captured using western blot assay.

Conclusions and implications:

ZFN might have off target on bacterial genome causing lethal double-strand DNA break due to lack of non-homologous end joining (NHEJ) mechanism. It is recommended to develop ZFNs against bacterial genes, engineered packaging host with NHEJ repair system is essential.

Dissecting the differential structural and dynamics features of CCL2 chemokine orthologs

Chemokines are a sub-group of cytokines that regulate the leukocyte migration. Monocyte chemoattractant protein-1 (MCP/CCL2) is one of the essential CC chemokine that regulates the migration of monocytes into inflamed tissues. It has been observed that the primary sequences of CCL2 orthologs among rodents and primates vary significantly at the C-terminal region. However, no structural details are available for the rodentia family CCL2 proteins. The current study unravelled the structural, dynamics and in-silico functional characteristics of murine CCL2 chemokine using a comprehensive set of NMR spectroscopy techniques and evolutionary approaches. The study unravelled that the N-terminal portion of the murine CCL2 forms a canonical CC chemokine dimer similar to that of human CCL2. However, unlike human CCL2, the murine ortholog exhibits extensive dynamics in the μs-ms timescales. The presence of C-terminal region of the murine CCL2 protein/rodentia family is highly glycosylated, completely disordered, and inhibits the folding of the structured CCL2 regions. Further, it has been observed that the glycosaminoglycan binding surfaces of these orthologs proteins are greatly differed. In a nut shell, this comparative study provided the role of molecular evolution in generating orthologous proteins with differential structural and dynamics characteristics to engage them in specific molecular interactions.