Key Role of Disulfide Bridges in the Antimicrobial Activity of Beta-Defensin from Olive Flounder
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Proteins that contain multiple disulfide bonds (SS bonds) expressed in Escherichia coli are usually problematic. This study reports the successful recombinant expression of the antimicrobial peptide β-defensin isolated from olive flounder in E. coli. The native form of β-defensin contained three discrete disulfide bridges: Cys1–Cys5, Cys2–Cys4, Cys3–Cys6. We constructed a periplasmic expression vector using small leading transmembrane protein YoaJ, and eventually, isolated bioactive β-defensin, which was then subjected to mass spectroscopy, circular dichroism spectroscopy, and anti-microbial testing. Results indicated bioactive β-defensin with a properly folded and native structure was formed. To investigate the roles of SS bonds, site-directed mutation method was applied to disrupt one, two, or three disulfide bridges. A dose-dependent effect was observed when more disulfide bridges were broken and a correlation between structure and function was observed, which further illustrated the key roles of SS bonds in maintaining the conserved motif and secondary structure of olive flounder beta-defensin.
KeywordsBeta-defensin Antimicrobial activity Disulfide bond Olive flounder
This research was supported by grants from the Marine Biotechnology Program (Grant No. 20170305; Development of Biomedical materials based on marine proteins) Funded by the Korean Ministry of Oceans and Fisheries, and from the National Fisheries Research and Development Institute, Korea (R2019016).
Compliance with Ethical Standards
Conflict of interest
The authors have no potential conflict of interest to declare.
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