FIGURE 6.

A homology model of the SKI-1/S1P prodomain structure. A, the proposed SKI-1/S1P prodomain model is depicted and colored with a gradient from blue (N terminus) to red (C terminus). For simplicity, nonstructured regions on the N and C termini of the prodomain model were omitted, and only the region from Gly³⁷ to Lys¹³⁷ is shown. A schematic of a typical αβ-plaid is also displayed. Circles represent α-helixes, and the rounded boxes represent the β-strands. Regions pointing in the opposite direction from the viewer are marked with a plus sign (N terminus), and those pointing toward the viewer are marked with an asterisk (C terminus). B, Coomassie-stained gel of purified recombinant prodomain AC. C, schematic representation of the human SKI-1/S1P prodomain in scale. Maturation sites B′/B and C′/C are indicated by yellow and magenta circles, respectively. On the upper panel, the secondary structures are indicated, as predicted by the psipred and RePROF prediction servers. The secondary structures of the model in Fig. 6A are added for comparison. The bottom part of the panel represents a conservation plot of the prodomain over 143 SKI-1/S1P orthologues. The y axis indicates the degree of conservation with a sliding window of five residues, green colored residues indicate 100% identity, brown colored residues indicate ≥30% <100%, and red colored residues indicate <30% identity.