FIG. 4.

Separation of membrane-bound Gag proteins by multilayer sucrose gradient flotation centrifugation. Membrane-bound Gag proteins were first isolated by 10%-65%-73% sucrose gradient flotation centrifugation followed by incubation at 37°C with or without 0.5% Brij 98 for 5 min. The samples were then assessed in a second round of flotation using the 10%-20%-30%-40%-50%-65% sucrose gradient. Twenty-one fractions were collected from the top of each gradient, and the distribution of Gag was assessed by Western blot using anti-p24 (capsid) antibodies. Relative levels of Gag are shown in the graph. The density of each fraction was measured by refractometer (Carl Zeiss). WT, wild type.