The effects of octylglucoside on the Semliki forest virus membrane. Evidence for a spike-protein--nucleocapsid interaction.

Evidence is presented for a non-covalent interaction between the spike glycoprotein and the nucleocapsid of Semliki Forest virus. When isolated viruses were treated with the non-ionic detergent beta-D-octylglucoside at neutral pH and low ionic strength the lipid bilayer membrane could be removed leaving most of the spike glycoproteins attached to the nucleocapsids. The interaction between capsids and membrane protein was sensitive to elevated pH and ionic strength, but at least partially reversible at neutral pH and low ionic strength. The possible role of this interaction in the viral structure and in the mechanism of budding of the virus from the host cell is discussed.