Fig. 1.

DmβUP crystal structure and mutation site environment in the homology model of human βUP. (a) Schematic view of homooctameric DmβUP with each subunit coloured differently. (b) Schematic view of a dimeric unit of DmβUP. For one of the subunits, β-strands are depicted in green, helices in yellow-green and loops in white, with the other subunit coloured salmon. Mutation sites are highlighted by space-filling models of the respective amino acid side chains in magenta. Labels first list the corresponding site in DmβUP. Location of the active site is indicated by space-filling models of the active site cysteine (C233 in human βUP, C234 in DmβUP) in yellow. (c-e) Enlarged views of I286T, G31S and E271K mutation sites. The homology model of human βUP is shown with different colours (salmon and green) for two separate subunits. Additional subunits were omitted as none of the mutations occur near putative interfaces. Stick models of side chains introduced by the mutations are shown in magenta, in preferred conformations causing the least clashes. Native side chains and residues surrounding the site are depicted with carbon atoms in the same colour as the subunit to which they belong. DmβUP side chains are shown with yellow carbon atoms when not conserved in human βUP. Labels indicate human βUP residues followed by corresponding DmβUP residues (if shown), with numbering for the latter only when it differs. Hydrogen bonds are indicated by dotted black lines. In (d), the loop directly following the G31S site is extended by one amino acid in DmβUP (shown in yellow). In (d) and (e), corresponding mutation sites in the second subunit of the dimer are marked by a magenta sphere in the background