Priming and Extending: a UbcH5/Cdc34 E2 Handoff Mechanism for Polyubiquitination on a SCF Substrate
Overview
Authors
Affiliations
We describe a mechanistic model of polyubiquitination by the SCF(beta TrCP2) E3 ubiquitin (Ub) ligase using human I kappaB alpha as a substrate. Biochemical reconstitution experiments revealed that the polyubiquitination of I kappaB alpha began with the action of the UbcH5 E2 Ub-conjugating enzyme, transferring a single Ub to I kappaB alpha K21/K22 rapidly and efficiently. Subsequently, the Cdc34 E2 functioned in the formation of polyubiquitin chains. It was determined that a Ub fused at I kappaB alpha K21 acts as a receptor, directing Cdc34 for rapid and efficient K48-linked Ub chain synthesis that depends on SCF(beta TrCP2) and the substrate's N terminus. The I kappaB alpha-linked fusion Ub appears to mediate direct contacts with Cdc34 and the SCF's RING subcomplex. Taken together, these results suggest a role for the multifaceted interactions between the I kappaB alpha K21/K22-linked receptor Ub, the SCF's RING complex, and Cdc34 approximately S approximately Ub in establishing the optimal orientation of the receptor Ub to drive conjugation.
Li M, Chen X, Qu P, Shao Z, Shi L, Quan H Proc Natl Acad Sci U S A. 2024; 121(45):e2402035121.
PMID: 39485803 PMC: 11551398. DOI: 10.1073/pnas.2402035121.
Mechanism of degrader-targeted protein ubiquitinability.
Crowe C, Nakasone M, Chandler S, Craigon C, Sathe G, Tatham M Sci Adv. 2024; 10(41):eado6492.
PMID: 39392888 PMC: 11468923. DOI: 10.1126/sciadv.ado6492.
Structure and dynamics of a pentameric KCTD5/CUL3/Gβγ E3 ubiquitin ligase complex.
Nguyen D, Rath D, Devost D, Petrin D, Rizk R, Ji A Proc Natl Acad Sci U S A. 2024; 121(17):e2315018121.
PMID: 38625940 PMC: 11047111. DOI: 10.1073/pnas.2315018121.
Cullin-RING ligases employ geometrically optimized catalytic partners for substrate targeting.
Li J, Purser N, Liwocha J, Scott D, Byers H, Steigenberger B Mol Cell. 2024; 84(7):1304-1320.e16.
PMID: 38382526 PMC: 10997478. DOI: 10.1016/j.molcel.2024.01.022.
Mechanism of millisecond Lys48-linked poly-ubiquitin chain formation by cullin-RING ligases.
Liwocha J, Li J, Purser N, Rattanasopa C, Maiwald S, Krist D Nat Struct Mol Biol. 2024; 31(2):378-389.
PMID: 38326650 PMC: 10873206. DOI: 10.1038/s41594-023-01206-1.