Spike glycoprotein cleavage recognition site analysis of infectious bronchitis virus.

The spike glycoprotein of infectious bronchitis virus (IBV), a coronavirus, is translated as a precursor protein (So), then cleaved into two subunits (S1 and S2) by host cell serine proteases. In this study, we compared the cleavage recognition site of 55 IBV isolates to determine if the cleavage recognition site sequence, which consists of five basic amino acid residues, correlates with host cell range, serotype, geographic origin, and pathogenicity as it does in orthomyxoviruses and paramyxoviruses. The most common cleavage recognition site observed (33 of 55 viruses) was Arg-Arg-Ser-Arg-Arg, representing at least 11 different serotypes.

Purified outer membranes of Serpulina hyodysenteriae contain cholesterol.

We have isolated outer and inner membranes of Serpulina hyodysenteriae by using discontinuous sucrose density gradients. The outer and inner membrane fractions contained less than 1 and 2%, respectively, of the total NADH oxidase activity (soluble marker) in the cell lysate. Various membrane markers including lipooligosaccharide (LOS), the 16-kDa outer membrane lipoprotein (SmpA), and the C subunit of the F1F0 ATPase indicated that the lowest-density membrane fraction contained outer membranes while the high-density membrane fraction contained inner membranes and that both are essentially free of contamination by the periplasmic flagella, a major contaminant of membranes isolated by other techniques.