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 86,000 and 66,000 mol. wt. The larger polypeptide was glycosylated.