Figure 5. Cross‐kingdom structural analysis of the OTU fold.

• A
  Cartoon representation of the EschOTU crystal structure colored in a rainbow gradient from N‐ to C‐terminus. The catalytic triad residues are marked on both the structure and the linear color gradient above, showing their positions with respect to each other and the overall OTU sequence. The black and gray arrows relate how the EschOTU fold is permutated with respect to other OTUs. The black open arrow marks the open N‐ and C‐termini, while the closed gray arrow marks a closed loop. OTU subfamilies that follow this overall sequence topology are listed in the lower right. This arrangement is only observed in EschOTU.
• B
  As in (A), for the human OTUB1 structure (PDB 4DDG). The closed black arrow marks a closed loop, while the open gray arrow marks the open N‐ and C‐termini. This arrangement is representative of the human Otubain, OTUD, and OTULIN subfamilies, as well as vOTUs.
• C
  As in (A), for the human Cezanne structure (PDB 5LRW). This arrangement is representative of the human A20 subfamily, viral PLP2, and Legionella ceg23.
• D
  As in (A), for the CCHFV vOTU structure (PDB 3PHW). A schematic for the permutated vOTU^P variant is shown to illustrate how it relates to the native sequence topology.
• E
  Ub‐PA activity‐based probe assay for WT vOTU and sequence‐permutated vOTU^P. Strong reactivity is indicated with asterisks.
• F
  Ub‐KG(TAMRA) cleavage assay monitored by fluorescence polarization for WT vOTU and sequence‐permutated vOTU^P.