Evaluation of the Expression of Recombinant Type A Botulinum Neurotoxin Light Chain Loaded onto a Cell-Penetrating Peptide

Botulinum toxin type A (BoNT/A) is widely used in the treatment of some muscle contraction disorders through injection. This study aimed to produce recombinant protein through covalent bonding of the light chain of BoNT/A to the peptide TAT (47-57), and to create an optimized condition for expression and purification of the protein. In this preliminary study, the nucleotide sequences of the light chain of BoNT/A and TAT peptide were obtained from Gen Bank, and genetic structures containing these sequences were designed and engineered. After cloning into the BL21 (DE3) E. coli vector, expression was induced by IPTG. Thereafter, optimum thermal condition and IPTG concentration for maximum expression were determined based on the difference in the intensity of staining between the bands on SDS-PAGE protein gel. The recombinant protein was purified through nickel column chromatography (Ni-NTA). The produced chimeric protein is insoluble in normal conditions (1 mM IPTG and at 37˚ C). Through optimization of expression conditions (0.5 mM IPTG and at 18˚ C) 60% of the chimeric protein was produced as solution. Based on our results, through expressing the recombinant protein as a solution, the protein maintained its proper folding and function. Hence, the use of denaturation compounds for solution making and destabilization of folded protein structures is not required.