Fig. 3
Paramagnetic relaxation enhancement NMR (PRE-NMR) analysis of intramolecular contacts. a PRE intensity ratio graphs (I ox/I red) of the Npm tail domain with MTSL paramagnetic spin labels at four different positions (positions indicated by arrows) and at two different NaCl concentrations (gray/red bars = 150 mM NaCl, orange points = 1 M NaCl). Error bars are inversely proportional to the propagated signal-to-noise ratio of individual resonances. Significant PRE effects (I ox/I red < 0.5) in the low-salt condition are highlighted in red. b Upper: I ox/I red graphs of the Npm tail domain bound to H2A/H2B. Two sets of intramolecular PRE effects derived from the complex (positions of spin labels indicated by arrows). Error bars are inversely proportional to the propagated signal-to-noise ratio of individual resonances. Same coloring scheme used as in a. Lower: Difference maps in I ox/I red values from the unbound and histone-bound states. Positive values indicate that residues are further from the spin label position after histone binding, negative values indicated that residues are closer to the spin label position after histone binding. c Intermolecular PRE effects measured using 1:1 molar ratio of non-isotope-labeled G132C-MTSL tail: 15N-labeled tail at 200 µM total protein concentration. Lack of strong PRE effects indicate very few or only transient intermolecular interactions. Error bars are inversely proportional to the propagated signal-to-noise ratio of individual resonances
