A Novel Signal Peptide Derived from Bacillus Licheniformis? -Amylase Efficiently Targets Recombinant Human Activin A to the Periplasm of Escherichia coli

Human activin A is a member of the transforming growth factor-β superfamily consists of two similar beta subunits. Activin A is expressed by different cells and displays numerous biological activities such as control of neuronal cell proliferation and differentiation, promotion of neuronal survival in the body. Therefore, recombinant production of activin A is beneficial because it can be used to treat many neurodegenerative diseases such as Alzheimer's and Parkinson diseases. In this study E. coli as a cheap and fast-growing host was selected to produce recombinant human activin A. As cytoplasmic expression of human activin A with complex structure and disulfide bonds produces inclusion bodies, so periplasmic expression of it can be beneficial. Therefore, we used modified Iranian B. licheniformis α-amylase signal peptide as a new signal peptide in order to translocate the recombinant activin A through the inner membrane. In this study human pro-activin A cDNA and signal sequence were cloned in pET21b vector and resulting vector transformed into the two strains of E. coli BL21. SDS-PAGE and western blot techniques were used to confirm recombinant activin A expression. Finally, our results indicated that the signal peptide used in this study was effective for secretion of activin A into the periplasmic space of E. coli.