Properties of Coronavirus IBV After Removal of the S1 Subunit of the Spike Glycoprotein
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Our recent investigations of avian infectious bronchitis virus (IBV) have concentrated on the biological properties of the spike (S) glycoprotein. Previously we showed that the mature S is derived by cleavage of a precursor glycoprotein to yield two glycopolypeptides, S1 and S2 of approximately 514 and 625 amino acid residues respectively1. Each spike comprises two or three copies of each of S1 and S2 the two subunits not being held to each other by disulfide bonds2, 3. The ease with which S1 but not the other virion proteins could be removed by urea or SDS 1ed us to suggest that S was anchored in the membrane by S2 and that S1 was probably not in the membrane but formed most of the distal, bulbous part of S3. This view was strengthened when sequencing of the S gene showed that S2 had a highly hydrophobic sequence, typical of membrane-spanning domains, near its carboxy terminus4.
KeywordsInfectious Bronchitis Virus Spike Protein Intact Virus Infectious Bronchitis Virus Strain Spike Glycoprotein
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