Recombinant production of isotope-labeled human α-defensin 5 via calmodulin fusion and insights into its expression enhancement.

Human α-defensin 5 (HD5), a cysteine-rich antimicrobial peptide critical for intestinal innate immunity, has been extensively studied for its structural and functional properties. Both the reduced form (HD5red) and the oxidized form (HD5oxi) exist in vivo and exhibit distinct antimicrobial activity spectra. In this study, we developed an efficient method to overexpress recombinant HD5 in Escherichia coli (E.