The Polypeptide Composition of Isolated Surface Projections of Avian Infectious Bronchitis Virus

Disruption of avian infectious bronchitis virus (IBV) particles with 4% Triton X-100 and 1.0 m-KCl and centrifugation through a sucrose gradient containing 0.1% Triton X-100 and 1.0 m-KCl enabled separation of the petal-shaped surface projections. By negative-contrast electron microscopy the separated projections appeared mainly as rosettes containing 3 to 12 projections radiating from a central core, although single projections and rosettes containing up to 16 projections were seen. SDS-PAGE of these preparations revealed two polypeptides of 86000 and 66000 mol. wt. The larger polypeptide was glycosylated.