(a) TsUCH37ΔC46 (in olive) ULD residues interacting with UbVME (in orange). Inset shows Arg261 and Tyr262 interactions with UbVME, as well as the intra-molecular salt bridge formed between Lys48 and Glu51 of ubiquitin. Density rendered from 2Fo-Fc map contoured to 0.7σ. (b-e) Comparison of the Lys48-Glu51 distance in ubiquitin observed in other DUB-ubiquitin structures. (b) Lys48 and Glu51 form a 3.7Å salt bridge in TsUCH37ΔC46 – UbVME structure (olive), but not in TsUCH37cat-UbVME structure (9.9 Å). (c) The same distance in all other UCH-ubiquitin structures are ≥9Å: UCHL3-UbVME in yellow (PDB ID 1XD3), UCHL1-UbVME in red (PDB ID 3KW5), Yuh1-Ubal in pink (PDB ID 1CMX), PfUCHL3-UbVME in purple (PDB ID 2WDT), TsUCH37cat-UbVME in teal. (d) The same distance in OTU-ubiquitin structures: Otu1-ubiquitin in dark red (PDB ID 3BY4) is 8.7 Å, and in DUBA-Ubal in pale yellow (PDB ID 3TMP) is 6.0 Å. (e) The same distance in HAUSP/USP7-Ubal (PDB ID 1NBF in blue) is 10Å and in USP14-Ubal (PDB ID 2AYO in brown) is 10.9Å.