FIG. 1.

Sites of VP7 mutations in VP7 helix 2. A cross section through the structure of the BTV core is shown with a VP7 trimer above the smooth VP3 subcore (above left). Helix 2 is indicated and shown in more detail viewed from the underside (above right). In the lower part of the the figure is an alignment of BTV and AHSV helix 2 residues, with grouping of the different mutations used to assess helix 2 function. Class I was derived from consideration of the homology; class II is equivalent to class I but with a deliberate change of residue character; class III shows a change of character at residues homologous between BTV and AHSV. Identical sequences are indicated by lines.