Experimental Evaluation of In Silico Selected Signal Peptides for Secretory Expression of Erwinia Asparaginase in Escherichia coli

Abstract

Erwinia chrysanthemi asparaginase is an important drug used in cancer treatment, especially in acute lymphoblastic leukemia (ALL). Escherichia coli periplasmic space is an ideal compartment for recombinant expression of certain proteins. To efficient secretion, an appropriate signal sequence should be chosen for each protein individually. In this study, the proper signal sequences for secretory production of Erwinia asparaginase were predicted by in silico methods. Consequently, two signal peptides, OmpA and DsbA, were selected for secretory expression of the enzyme in E. coli. Asparaginase was translocated through the cytoplasmic membrane with either DsbA signal peptide or OmpA signal peptide; Using DsbA signal peptide, 5.95 units of the enzyme was obtained per milliliter of culture media, whereas OmpA signal sequence led to some amount of periplasmic expression. Our study showed that the co-translational signal peptide, DsbA, targeted the asparaginase to cell membrane more efficiently in comparison to the post-translational signal peptide, OmpA. The combination of in silico and experimental approaches provides a way to test a wide variety of signal sequences for secretory production of the enzyme in a time- and cost-effective manner. It is a fundamental step for further studies in the enzyme production process.