28mk | pdb_000028mk
Cryo-EM structure of UBA6 in complex with FAT10 in the post-thiolation state.
Structural highlights
FunctionUBA6_HUMAN Activates ubiquitin by first adenylating its C-terminal glycine residue with ATP, and thereafter linking this residue to the side chain of a cysteine residue in E1, yielding a ubiquitin-E1 thioester and free AMP. Specific for ubiquitin, does not activate ubiquitin-like peptides. Differs from UBE1 in its specificity for substrate E2 charging. Does not charge cell cycle E2s, such as CDC34. Essential for embryonic development. Required for UBD/FAT10 conjugation. Isoform 2 may play a key role in ubiquitin system and may influence spermatogenesis and male fertility.[1] [2] [3] Publication Abstract from PubMedAttachment of the ubiquitin-like protein (UBL) FAT10 onto substrates targets them for proteasomal degradation. Like ubiquitin, FAT10 is activated by the E1 enzyme UBA6 then transferred to E2 enzymes, but mechanisms controlling ubiquitin versus FAT10 activation by UBA6 and FAT10 transfer onto E2s remain unclear. Using cryo-EM, we visualise all stages of FAT10 E1-E2 handover: adenylation, thiolation and transthiolation. We find that FAT10 monopolises UBA6 by out-competing ubiquitin for thiolation and blocking the adenylation domain, preventing further UBL recruitment and promoting FAT10 signalling. We profiled UBA6-compatible E2 enzymes and found FAT10 transfer is restricted to a select subset associated with specific cellular pathways. UBE2Z (USE1) showed highest activity followed by UBE2D2, UBE2J2 and UBE2S. Capturing FAT10 or ubiquitin transfer from UBA6 to UBE2Z reveals UBE2Z is highly specialised for FAT10 transfer. It simultaneously engages both FAT10 domains (UBL1 and UBL2) and co-ordinates the metabolite inositol hexakisphosphate (InsP(6)) bound within the UBA6 catalytic domain. This InsP(6) co-ordination extends to other FAT10 compatible E2s. Together, our structural and biochemical analyses reveal regulatory mechanisms underpinning FAT10 activation and transfer. We define principles governing selective FAT10 transfer, highlighting favourable interactions with FAT10 C-terminal domain (UBL2) and stable UBA6 binding, ensuring controlled conjugation onto substrates. Structural determinants for FAT10 activation and transfer from UBA6 to E2 enzymes.,Ellison CJ, Riechmann C, Dalietou EV, Simmons MDR, Dodd EC, Elliott PR Nat Commun. 2026 Aug 13;17(1):9751. doi: 10.1038/s41467-026-76603-3. PMID:42733088[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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