Figure 2: Crystal structure of 1A-310-677aa.

(a, top) Ribbon model of 1A-310-677aa; bottom: schematic diagram of 1A-310-677aa. The core subdomain is shown in blue, the insertion loop is shown in magenta, and SD-1 subdomain is shown in green. Twelve pairs of disulfite bridges are numbered and shown in yellow and stick model. The amino acid numbers are from the S protein of the genotype A HKU1 virus. (b) Schematic illustration of the topological graph of 1A- 310-677aa. β-strands are shown with brown arrows, α-helices are shown with bright blue cylinders.