Fig. 3: Structural analysis of UBE1L specificity.
From: Insights into the ISG15 transfer cascade by the UBE1L activating enzyme
a Left, cryo-EM density of adenylated ISG15 bound to UBE1L. Right, close-up view of the adenylated ISG15 C-terminus within the adenylation domain (AD) active site (also see Supplementary Fig. 5f). b UBE1L-ISG15 surface contacts. The circled area corresponds to the primary contact site between ISG15 and UBE1L. Amino acid side chain interactions within the interface are shown in c. c ISG15 and AD interactions. The Thr125 patch of ISG15 (Thr125, Phe149, Asn151 – analogous residues to the Ile44 patch of ubiquitin; also see Supplementary Fig. 5g) contact residues within the AD (Tyr885, Tyr892, Ile894). Additional hydrophobic residues of ISG15 (Trp123, Pro130) contact UBE1L (Tyr896). d UBE1L recognition of UBE2L6. Circled area corresponds to the primary contact site between the ubiquitin fold domain (UFD) of UBE1L and UBE2L6. The second catalytic cysteine half-domain (SCCH) of UBE1L also contacts UBE2L6. Amino acid side chain interactions within the UFD-UBE2L6 interface are shown in e. e UBE2L6 and UFD interactions. A hydrophobic surface of the UFD (Ile945, Leu947, Leu952) coordinates UBE2L6 helix-1 residues (Met5, Val8).
