Ubiquitin-conjugating enzyme Cdc34 and ubiquitin ligase Skp1-cullin-F-box ligase (SCF) interact through multiple conformations.

In the ubiquitin-proteasome system, protein substrates are degraded via covalent modification by a polyubiquitin chain. The polyubiquitin chain must be assembled rapidly in cells, because a chain of at least four ubiquitins is required to signal for degradation, and chain-editing enzymes in the cell may cleave premature polyubiquitin chains before achieving this critical length. The ubiquitin-conjugating enzyme Cdc34 and ubiquitin ligase SCF are capable of building polyubiquitin chains onto protein substrates both rapidly and processively; this may be explained at least in part by the atypically fast rate of Cdc34 and SCF association. This rapid association has been attributed to electrostatic interactions between the acidic C-terminal tail of Cdc34 and a feature on SCF called the basic canyon. However, the structural aspects of the Cdc34-SCF interaction and how they permit rapid complex formation remain elusive. Here, we use protein cross-linking to demonstrate that the Cdc34-SCF interaction occurs in multiple conformations, where several residues from the Cdc34 acidic tail are capable of contacting a broad region of the SCF basic canyon. Similar patterns of cross-linking are also observed between Cdc34 and the Cul1 paralog Cul2, implicating the same mechanism for the Cdc34-SCF interaction in other members of the cullin-RING ubiquitin ligases. We discuss how these results can explain the rapid association of Cdc34 and SCF.

Sandoval D ，Hill S ，Ziemba A ，Lewis S ，Kuhlman B ，Kleiger G ... -  《-》

Rapid E2-E3 assembly and disassembly enable processive ubiquitylation of cullin-RING ubiquitin ligase substrates.

Kleiger G ，Saha A ，Lewis S ，Kuhlman B ，Deshaies RJ ... -  《-》

The acidic tail of the Cdc34 ubiquitin-conjugating enzyme functions in both binding to and catalysis with ubiquitin ligase SCFCdc4.

Kleiger G ，Hao B ，Mohl DA ，Deshaies RJ ... -  《-》

Cdc34 C-terminal tail phosphorylation regulates Skp1/cullin/F-box (SCF)-mediated ubiquitination and cell cycle progression.

Sadowski M ，Mawson A ，Baker R ，Sarcevic B ... -  《-》

Identification of Elongin C and Skp1 sequences that determine Cullin selection.

Yan Q ，Kamura T ，Cai Y ，Jin J ，Ivan M ，Mushegian A ，Conaway RC ，Conaway JW ... -  《JOURNAL OF BIOLOGICAL CHEMISTRY》