Bioprocessing of human beta defensin-25

Abstract

Anti-microbial peptides are cationic and amphiphilic peptides that have anti-microbial properties against a variety of bacteria and fungi. An important class of anti-microbial peptides is human β defensins (HBD), which have the potential to replace classic antibiotics due to their difference in anti-microbial mechanisms and strong anti-microbial activity. The aim of this project was to develop a bioprocess for recombinant production of HBD-25 from E. coli. HBD-25 is endogenously found in the epithelial cell layer of the testis and epididymis and is predicted to play an important role in genital tract infections. Expression of HBD-25 in the form of a fusion protein in E. coli cells resulted in soluble aggregate formation. To render the protein monomeric, the fusion protein was refolded using Size Exclusion Chromatography (SEC) before cleavage to recover the HBD-25. Preliminary indication of refolding success was characterized by the use of SEC and SDS-PAGE analysis. The effect of varying refolding concentrations on fusion protein refolding yield was also studied. The refolded fusion protein was then cleaved with the Tobacco Etch Virus (TEV) protease and analysed for recovery of monomeric HBD-25 using SEC.