FIGURE 1. The X-ray structure of the monomeric subunit of NSP2.

a, A stereo view of the ribbon representation of the structure. The secondary structural elements in the monomer are coloured: -helices in red, -strands in green and loops in blue. The locations of the major -helices are indicated following the same numbering scheme as in c. The basic loop between the subdomains in the N-terminal domain is shown by an arrow. b, Another view of the monomer showing the cleft (arrow) and the domain organization. The N- and C-terminal domains are shown in green and red respectively. The location of the N and the C termini are denoted in both a and b. c, The structure–sequence relationship in NSP2. The secondary structural elements along with the sequence are shown following the same colour scheme as in a. -helices and -strands are numbered sequentially. The strictly conserved residues are highlighted in orange. The residues that participate in the 4- and 2-fold contacts of the octamer are indicated by boxes below the sequence in blue and purple respectively. The HIT-homology (see Fig. 2) region is underlined in light blue.