Antioxidant activities of recombinant amphioxus (Branchiostoma belcheri) apolipoprotein D

Apolipoprotein D (ApoD), a member of lipocalin, has been recently shown to be involved in regulating protection from oxidative stress. The absence of ApoD in mouse and Drosophila can reduce the resistance to oxidative stress and shorten lifespan. However, little information is available regarding the expression in vitro of ApoD and its biochemical properties. Amphioxus (Branchiostoma belcheri) ApoD, BbApoD, is an archetype of vertebrate ApoD proteins. In this study, the prokaryotic expression plasmid pET32a-BbApoD was constructed and recombinant BbApoD expressed in Escherichia coli BL21 and purified. Antioxidation assays showed that the recombinant BbApoD protein had the capacities to scavenge hydroxyl radicals (≥ 240 μg/ml) and to prevent nicking of the supercoiled DNA (≥ 100 μg/ml) in vitro, providing a biochemical evidence for antioxidant role of ApoD. This supports the notion that ApoD is part of the mechanisms regulating protection from oxidative stresses.