Effect of Phosphorylation on the Structural Behaviour of Peptides Derived from the Intrinsically Disordered C‐Terminal Domain of Histone H1.0

To investigate the structural impact of phosphorylation on the human histone H1.0 C‐terminal domain, we performed NMR structural studies of model peptides containing a single phosphorylation site: T118‐H1.0 (T118PKK motif) and T140‐H1.0 (T140PVK motif). Both model peptides are mainly disordered in aqueous solution in their non‐phosphorylated and phosphorylated forms, but become structured in the presence of trifluoroethanol. The peptides T118‐H1.0 and pT118‐H1.0 contain two helical regions, a long amphipathic α helix spanning residues 104–115 and a short α/310 helix (residues 119–123), that are almost perpendicular in T118‐H1.0 but have a poorly defined orientation in pT118‐H1.0. Peptides T140‐H1.0 and pT140‐H1.0 form very similar α helices between residues 141–147. The TPKK and TPVK motifs show the same backbone conformation, but differ in their side‐chain contacts; the Thr and pThr side chains interact with the i+2 Lys side chain in the TPKK motif, and with the i+3 Lys side chain in the TPVK motif. The pT phosphate group in pT118‐H1.0 and pT140‐H1.0 has pKa values below the intrinsic values, which can be explained by non‐specific charge–charge interactions with nearby Lys. The non‐polar Val in the TPVK motif accounts for the pT140 pKa being closer to the intrinsic pKa value than the pT118 pKa. Altogether, these results validate that minimalist strategies using model peptides can provide structural details difficult to obtain in short‐lived intrinsically disordered proteins and domains.