Soluble fusion expression, characterization and localization of human β-defensin 6

Human β‑defensin 6 (DEFB106) is an antimicrobial peptide expressed in the epididymis, testis and lung, which indicates that DEFB106 may be involved in innate immunity and fertility. However, as a β‑defensin, this protein has not been well characterized. Using an intein‑mediated fusion expression system, the recombinant DEFB106 was expressed and purified (yield, 3‑5 mg/l) under optimized conditions. The purified protein was characterized using mass spectrometry and circular dichroism spectroscopy. The measured molecular weight was consistent with its theoretical value and the predominant secondary structure was β‑sheet, the common structure of β‑defensin family members. The purified DEFB106 showed antimicrobial activity against not only Escherichia coli (E. coli) and Candida albicans (C. albicans) SC5314, but also Staphylococcus aureus (S. aureus) CMCC26003. Furthermore, it exhibited a high affinity for heparin and lipopolysaccharide. In addition, it was determined that native DEFB106 was located in the epididymis, bone marrow and skin. These observations may aid in the determination of the physiological and pathological functions of DEFB106.