Isolation of the glycoprotein of vesicular stomatitis virus and its binding to cell surfaces

The glycoprotein (G) of vesicular stomatitis virus (VSV) was radiolabelled, extracted and purified so that its potential interaction with host cell surfaces could be studied. When BHK-21 cells were incubated with the radiolabelled virus glycoprotein, the virus component rapidly attached to the cell surface. The attachment was shown to be temperature-dependent adn saturated at approx. 3 X 10(5) molecules/cell. The omission of Mg2+ or Ca2+ from the incubation medium had little effect on the glycoprotein binding. Treating the isolated G protein and intact virions with neuraminidase did not significantly decrease their binding to BHK-21 cells. Pre-incubating cells with trypsin did not decrease the attachment of VSV virions nor the binding of purified G protein. Treating cells with phospholipase A or phospholipase C suggested that the binding of the glycoprotein and the intact virion might have been dissimilar. Unlabelled glycoprotein competitively inhibited binding of the labelled molecules although the presence of intact virions did not inhibit attachment of the G protein. Likewise, saturating amounts of the glycoprotein did not decrease binding of VSV to BHK-21 cells. These observations suggested that either the isolated glycoprotein bound to cell surface components that were distinct from the virion receptor or that the manner of the purified glycoprotein attachment differed from the G protein still associated with the intact virion. Chemical crosslinking and diagonal two-dimensional gel electrophoresis were used to identify and to compare the cell surface components responsible for glycoprotein and virion attachment.