The polypeptides of infectious bronchitis virus (IBV-41 strain)

The Massachusetts strain of avian infectious bronchitis virus was purified from embryonated hens' eggs. Four major species of apparent mol. wt. 90 000, 52 000, 29 000 and 26 000 were resolved by SDS-polyacrylamide gel electrophoresis. Omission of reducing agent failed to resolve the 29 000 mol. wt. component. Labelling of acrylamide gels with 125I-concanavalin A indicated that polypeptides of mol. wt. 90 000, 29 000 and 26 000 were glycosylated and, in the absence of reducing agent, that the 29 000 species migrated as a dimer in the 5000 mol. wt. region. Purified IBV radio-iodinated with Bolton and Hunter reagent, which banded as a single peak of radioactivity in Metrizamide gradients, was found to contain bands of radioactivity when analysed by SDS-PAGE, corresponding to the polypeptides of mol. wt. 90 000, 52 000 and 29 000 resolved in stained gels. Disruption of IBV particles in Triton X-100 released two subviral particles, a 16 nm spike which comprised polypeptides of 90 000, 52 000 and 29 000 mol. wt. and another denser spherical particle of 25 to 45 nm which contained RNA and the 52 000 and 26 000 polypeptides.