Figure 1.

H3 tail conformation is distinct between nucleosomal species. (A) Overlay of ¹H/¹⁵N-HSQC spectra collected on ¹⁵N-H3-labeled versions of the three nucleosomal species, nucleosome (black), hexasome (blue) and tetrasome (red). Comparison of the spectra indicates that the H3 tail exists in different conformational ensembles between the nucleosome and tetrasome and suggests that hexasome contains one copy of H3 in a similar conformational ensemble as nucleosome and one copy of H3 in a similar conformational ensemble as tetrasome. Expanded regions of the overlay are shown for selected residues for closer comparison of histone tail states. Small circles mark the approximate center of each peak to aid in the spectral comparison. These spectra were collected on 44 μM ¹⁵N-H3 nucleosomal species in 20 mM MOPS pH 7, 1 mM EDTA, 1 mM DTT, 7% D₂O at 37°C and on an 800 MHz spectrometer. (B) Chemical shift differences (Δδ) between the nucleosome and tetrasome H3 tails (top), the nucleosome and hex-N H3 tails (center), and the tetrasome and hex-T H3 tails (bottom). This plot is shown as a function of H3 tail residue.