Membrane-destabilizing activity of rotavirus NSP4 is mediated by a membrane-proximal amphipathic domain

Expression of the rotavirus non-structural glycoprotein NSP4 in E. coli leads to a decrease in optical density of the culture and release of [(3)H]uridine into the medium, effects attributable to the ability of NSP4 to perturb the bacterial membrane. To identify a domain of NSP4 responsible, different regions of the polypeptide were expressed in E. coli. Membrane destabilization is associated with a region of the protein located within residues 48-91, which includes a potential cationic amphipathic helix. A second region of NSP4 that contains a coiled-coil oligomerization domain and a sequence reported to function as a viral enterotoxin enhances the membrane-destabilizing activity of residues 48-91, but has no direct effect on the membrane stability. These studies suggest that the membrane-destabilizing and enterotoxic properties of NSP4 may be mediated by different regions of the polypeptide and suggest a possible basis for the cytotoxicity of NSP4 in mammalian cells.