Figure 6: Model: ubiquitylation regulates Rpn10 dissociation from the proteasome.
From: Structure of ubiquitylated-Rpn10 provides insight into its autoregulation mechanism
Schematic model for the regulation of Rpn10 by ubiquitylation: (I) Apo-Rpn10 (purple) is bound to the proteasome. Rpn9, pink; Rpn8, light blue; Rpn11, cyan; non-covalent Ub-binding patch, yellow; Rpn10:Rpn9 interface, green. (II) Ub∼Rsp5 interacts with the non-covalent Ub-binding patch on vWA. Ub, orange; Ub-G76, red; Rpn10-K84, blue. (III) In the non-covalent interaction, the C terminus of Ub is located in proximity to K84. (IV) Upon ubiquitylation, the Ub moiety, covalently linked to K84, assumes a lower-energy conformation (the black background is intended to facilitate perception of Ub motion). (V) The Ub moiety clashes with Rpn9 and ejects Ub-Rpn10 from the proteasome. Dissociation of Ub-Rpn10 from the proteasome was recently demonstrated by Crosas and co-workers39. Debiquitylation probably returns Rpn10 to its apo-free form and allows a next cycle of Rpn10-dependent ubiquitylated substrate degradation.
