Structures of the KUPEV and GANV OTUs in complex with sheep ISG15.
(A) A cartoon rendering of the KUPEV OTU (green) bound to the C-terminal domain of sheep ISG15 (purple). The propargylamine molecule covalently linking the ISG15 and OTU is shown in brown. The regions of the OTU forming the interface with sheep ISG15 are indicated by a shaded background. The approximate locations of residues forming the selectivity pocket are indicated by red dots. The secondary structure for KUPEV OTU as calculated by the DSSP server is indicated . (B) A cartoon rendering of the GANV OTU (orange) bound in complex with sheep ISG15 (purple), annotated as in (A). (C-D) Closeup views of major interactions within the three main regions (I-III) and peripheral regions (P) of the KUPEV/GANV interface with sheep ISG15. Black dashes indicate interatomic distances ≤3.5 Å between atoms capable of forming electrostatic pairs. (E) A closeup of residue 122 in the KUPEV and GANV OTUs, with the impact of mutating this residue measured by activity towards Ub-AMC and human ISG15-AMC. Values are the mean ± standard deviation of two independent experiments.