Expression analysis of a highly soluble region of an enterotoxigenic non-structural protein of bovine rotavirus

Abstract

Rotaviruses of group A (RVA) are foremost cause of diarrhoeal diseases in neonates of animals and humans worldwide leading to substantial economic losses. The RVA non-structural protein-4 (NSP-4), a viral enterotoxin, is known to be associated with infantile gastroenteritis/secretory diarrhoea by inducing pathological changes in the mature enterocytes. In this study, the carboxyl terminus of NSP4 protein (73M to 175M) from a bovine RVA was expressed in Escherichia coli Tuner (DE3) pLysS cells. The fusion protein (rNSP4ct, ~31 kDa) with hexa-histidine tags on its both termini was purified by affinity chromatography under native condition using Nickel-Nitrilotriacetic acid (Ni-NTA) agarose resin. The purified soluble recombinant NSP4ct was confirmed by Western blot. The structural analysis of rNSP4 protein revealed similarity between bovine RVA and human RVA (central tetrameric coiled-coil region) and confirmed that it was composed of mainly alpha helix (85%), lacking the beta strands. The rNSP4ct protein of bovine RVA has the potential of being used in developing diagnostics, assessing the biological activity (enterotoxin property) of rNSP4ct in understanding the pathogenesis in intestinal mucosa which would reveal the role of anti-NSP4 antibodies in protection against rotavirus infection and stimulation of mucosal immunity in animal model.