Editing Proteasome (section)

===== Rpn1 =====
Ubiquitin binds Rpn1 via two sites, termed the T1 and T2 sites that were identified using NMR.<ref name="Shi">{{cite journal | vauthors=Shi Y, Chen X, Elsasser S, Stocks BB, Tian G, Lee BH, Shi Y, Zhang N, de Poot SA, Tuebing F, Sun S, Vannoy J, Tarasov SG, Engen JR, Finley D, Walters KJ | title = Rpn1 provides adjacent receptor sites for substrate binding and deubiquitination by the proteasome | journal = Science | volume = 351 | date = Feb 2019 | issue = 6275 | pmid = 26912900 | doi = 10.1126/science.aad9421 | pmc = 4980823 }}</ref>  Rpn1 also provides a docking site for Ubp6.

The affinities for ubiquitin for these receptors in isolation has been measured through a variety of methods.  They are all in the micromolar range, however a substrate that has both a ubiquitin signal and an unstructured region has a [[Michaelis menten]] constant in the hundreds of nanomolar range, suggesting that the unstructured region in key in engaging a substrate.
{| class="wikitable"
|+Reported binding constants to Ubiquitin or K48 Ub2
!Receptor
!Ligand
!Published Kd (method of measurement)
!Reference
|-
|'''Rpn1'''
|Ub
|120 uM (NMR [[Nuclear magnetic resonance spectroscopy]])
|Shi ''Science'' 2016
|-
|'''Rpn1'''
|K48 Ub<sub>2</sub>
|11 uM (NMR, ITC [[Calorimetry|Isothermal Calorimetry]])
|Shi ''Science'' 2016
|-
|'''Rpn13'''
|Ub
|91 uM (SPR [[Surface plasmon resonance]])
|VanderLinden ''JBC''2017
|-
|'''Rpn13'''
|K48 Ub<sub>2</sub>
|29 uM(NMR)

37 uM (ITC)
|Chen ''Structure'' 2016

VanderLinden ''JBC'' 2016
|-
|'''Rpn10 UIM'''
|Ub
|45 uM (NMR)

43 uM (SPR)
|Chen ''Structure'' 2016
|-
|'''Rpn10 UIM'''
|K48 Ub<sub>2</sub>
|13 uM (SPR)
|Zhang ''Mol Cell'' 2009
|}