Ebola virus: identification of virion structural proteins

Abstract

Polyacrylamide gel electrophoresis of purified Ebola virus revealed the presence of four major virion structural proteins which we have designated VP1, VP2, VP3 and VP4. Vesicular stomatitis virus (VSV) proteins were used as mol. wt. markers, and the virion proteins were found to have mol. wt. of 125000 (VP1), 104000 (VP2), 40000 (VP3) and 26000 (VP4). VP1 was labelled with glucosamine and is probably a glycoprotein. The density of the Ebola virion was approx. 1.14g/ml in potassium tartrate. Virus nucleocapsids with a density of 1.32g/ml in caesium chloride were released when virions were treated with detergents. Proteins VP2 and VP3 were consistently associated with released nucleocapsids and are probably the major structural nucleocapsid proteins analogous to the N protein of VSV. Protein VP4 was reduced or absent in released nucleocapsids and is probably analogous to the membrane (M) protein of VSV and similar viruses. The glycoprotein (VP1) is larger than the glycoprotein of any known negative-strand RNA virus and is not labelled well with 35S-methionine. VP1 is solubilized by detergent treatment, suggesting that it is a component of the virion spikes and analogous to the G protein of VSV. Our results, in conjunction with analysis of Ebola virion RNA (Regnery et al. 1980), strongly suggest that the virus is a negative-strand RNA virus and, along with marburg virus, may constitute a new taxon within this group.