Expression of recombinant viscum album coloratum lectin B-chain in the silkworm expression system and evaluation of antioxidant activity

Korean mistletoe lectins (KMLs) possess many biological activities, including anti-tumor, apoptosis-inducing, anti-metastatic, and anti-angiogenic activities. Recombinant KML-1A (rKML-1A) has been previously expressed in soluble form in Escherichia coli cells. However, the expression of rKML-1B in soluble form remains to be accomplished. In this study, we describe the production, purification, and characterization of recombinant KML-1B by using a baculovirus expression system, which employs silkworm larvae and pupae as hosts. Approximately 495 and 702 µg/mL of a 36-kDa rKML-1B protein were produced without a signal peptide by silkworm larvae and pupae, respectively. Treatment of the recombinant protein with N- or O-deglycosylase led to a decrease in its molecular mass, indicating the N-and/or O-glycosylation of rKML-1B. Purified rKML-1B displayed radical scavenging activities toward 1,1-diphenyl-2-picrylhydrazyl and 2,2′-amino-di-[3-ethylbenzthiazoline sulfonate], with a half maximal inhibitory concentration (IC50) of approximately 95 µg/mL. This activity was discovered to be stable at 65°C. To our knowledge, this is the first report detailing the biological activity of plant-derived, pure rKML-1B.