C-Cbl-UbcH7 complex

Zheng, N., et al.. Structure of a c-Cbl-UbcH7 complex RING domain function in ubiquitin-protein ligases. Cell, 2000, 102(4), 533-9. 

Fig. S.S. UbcH7/c-Cbl complex (IFBV).The surface of UbcH7 is shown with residues interacting with the c-Cbl RING domain shown in red and the active-site cysteine shown in yellow. c-Cbl is colored green.

The surface of UbcH7 that contacts c-Cbl does not overlap with the E2 surface that contacts ubiquitin (Figures. 5.4 and 5.5 see also Ref [108]), confirming that the E2/ubiquitin thiol ester can associate with a RING E3. The E2 surface that contacts c-Cbl does, however, overlap the E2 surface implicated in E1/E2 interactions (Section 5.6.1). Thus, the El may have to depart from the E2/ubiquitin complex before E2/E3 interactions can take place. 

A model of the full SCF/E2 complex [112] shows that the end of Skp2 which binds the substrate is pointed toward the Rbxl-bound E2, with a 50-A gap between the two. Models based on two other SCF structures show similar distances between the F-box protein and the E2 [109, 115]. Whether this gap can be bridged by the bound substrate is currently unclear. It has been suggested that the E2 may bind to Rbxl somewhat differently than UbcH7 is observed to bind in the c-Cbl RING/ UbcH7 complex, but it is not obvious that this can lead to a 20 A movement of the E2 toward the bound substrate as suggested [109]. 

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