Figure 4. Canonical ubiquitin receptors and their locations on the proteasome.

The locations of the two well-characterized ubiquitin receptors on the proteasome, Rpn10 (blue) and Rpn13 (cyan), together with the organizing subunit Rpn1 (dark orange) and the deubiquitinase Rpn11 (purple) are highlighted. The remaining proteasome subunits are shown in grey. The locations of Rpn10 and Rpn13 might allow a polyubiquitin chain to bind both receptors simultaneously or they serve as an adaptive platform to feed structurally diverse substrates into the translocation motor (left). Rpn1 provides a docking site for UbL-UBA proteins such as Rad23 that deliver substrates to the proteasome. The figure was generated using the EM structure (EMD-1992) from Lander et al 2012 and atomic coordinates from Beck 2012 pdb file (PDB code: 4B4T)^{65, 68} using Chimera and Segger as in Figure 2^{154, 155}.