Identification of a New Membrane-associated Polypeptide Specified by the Coronavirus Infectious Bronchitis Virus

Nucleotide sequences from the third open reading frame of mRNA D (D3) of infectious bronchitis virus (IBV) were expressed in bacteria as part of a fusion protein with β-galactosidase. Antiserum raised in rabbits against this fusion protein immunoprecipitated from IBV-infected chick kidney or Vero cells a polypeptide of 12.4K, the size expected for a D3-encoded product. The D3 polypeptide is apparently non-glycosylated, and appears to be associated with the membrane fraction of infected cells, as judged by cell fractionation and immunofluorescence.