Ubiquitin-conjugating Enzyme Cdc34 and Ubiquitin Ligase Skp1-Cullin-F-box Ligase (SCF) Interact through Multiple Conformations

Suramin inhibits cullin-RING E3 ubiquitin ligases

“…Canonical cullins 1-5 share a conserved, C-terminally located basic canyon (15). Indeed, recent work has demonstrated direct binding of the CUL2 basic canyon to the Cdc34 C-terminal tail (16). In further support, the biochemical reconstitution assays have revealed that a variety of CRL complexes tested, including ROC1-CUL2, ROC1-CUL3, and ROC1-CUL4A, can support Cdc34 for di-Ub synthesis (Fig.…”

“…Cullins 2-5 (CUL2-5) share a conserved, C-terminally located basic canyon originally identified in CUL1 (15). In support, a more recent work revealed direct binding of the CUL2 basic canyon to the Cdc34 C-terminal tail (16). Given the evidence that suramin targets CUL1's basic pocket (Fig.…”

“…1A) exclusively carrying a K48 linkage (13). ROC1 binds to the Cdc34 catalytic core domain (14), whereas the CUL1 CTD provides a basic pocket that interacts with Cdc34's acidic C terminus, thereby facilitating E2 recruitment (15,16).…”

“…Using a chimera strategy, yeast genetic studies have shown that fusion of the Cdc34 acidic C-terminal tail to another E2 (such as Ubc2/Rad6) can transform the chimeric enzyme into a Cdc34-like protein essential for supporting cell growth, underscoring an indispensable role for the E2's negatively charged C terminus (35,36). Subsequent biochemical experiments have demonstrated the interactions between Cdc34 and E3 SCF (CRL1) (37), mapped the binding activity to the E2 acidic C terminus and E3's ROC1-CUL1 CTD subcomplex (38), and finally localized the contacts to CUL1 CTD's basic canyon and the E2 negatively charged C-terminal tail (15,16). Canonical cullins 1-5 share a conserved, C-terminally located basic canyon (15).…”

“…The CRL superfamily, which contains ∼300 members and accounts for nearly half of the E3s identified in humans, affects a myriad of biological processes by directing numerous protein substrates for proteasomal degradation (2,3). Key to CRL activity is the recruitment of the E2 Cdc34 through electrostatic interactions between E3's cullin conserved basic canyon and the acidic C terminus of the E2 enzyme (15,16). Cdc34 is the only E2 required for cell viability in yeast (34).…”