Interactions of Vesicular Stomatitis Virus Structural Proteins with HeLa Plasma Membranes

THE processes whereby nucleoprotein core particles of certain animal viruses become enveloped by and bud off from host cell membranes can be studied by preparing membrane^1,2 or “sedimentable”³ fractions from infected cells and examining them for the presence of virus proteins. We find that similar experiments designed to monitor assembly of vesicular stoma-titus virus (VSV) at sites along the plasma membranes of HeLa cells are best interpreted after first investigating the possibility that virus proteins adsorb to plasma membranes during cell fractionation and membrane isolation. In this report, we show that at 0° C the membrane protein of VSV, among other virus proteins, adsorbs to plasma membranes isolated from uninfected HeLa cells. With appropriate pulse-chase experiments, however, we are able to demonstrate the progressive association, in vivo, of VSV core protein with plasma membranes of infected HeLa cells.