Figure 3. Ensemble refinement of the closed-state structure of K63-Ub2 against intra-molecular inter-subunit paramagnetic relaxation enhancements (PREs).
(A) Heat map of PRE Q-factor upon varying the number of conformers and the population of the closed state. (B) The correlation between observed and calculated PREs, with a four-conformer representation at 70% closed-state population. The PRE ensemble Q-factor is 0.26 and 0.18 for the N25C site (open circles) and K48C site (closed circles), respectively, and 0.22 for both sites. The diagonal indicates a perfect correlation to guide the eyes.
Figure 3—figure supplement 1. Cross-validation of paramagnetic relaxation enhancement (PRE) data.
The closed-state structure of K63-Ub2 was refined against N25C data only with a four-conformer representation. The PREs for the K48C site were back-calculated (blue line), which agree well with the experimental data (red circles) with a free Q-factor of 0.46. Residues that are completely broadened out are denoted with asterisks at the top.