Assignment of the disordered, proline-rich N-terminal domain of the tumour suppressor p53 protein using 1HN and 1Hα-detected NMR measurements

Protein p53 is mostly known for playing a key role in tumour suppression, and mutations in the p53 gene are amongst the most frequent genomic events accompanying oncogenic transformation. Continuous research is conducted to target disordered proteins/protein regions for cancer therapy, for which atomic level information is also necessary. The disordered N-terminal part of p53 contains the transactivation and the proline-rich domains—which besides being abundant in proline residues—contains repetitive Pro-Ala motifs. NMR assignment of such repetitive, proline-rich regions is challenging due to the lack of amide protons in the ¹H^N-detected approaches, as well as due to the small chemical shift dispersion. In the present study we perform the full assignment of the p53^1–100 region by applying a combination of ¹H^N- and ¹H^α-detected NMR experiments. We also show the increased information content when using real-time homo- and heteronuclear decoupled acquisition schemes. On the other hand, we highlight the presence of minor proline species, and using Pro-selective experiments we determine the corresponding cis or trans conformation. Secondary chemical shifts for (C^α–C^β) atoms indicate the disordered nature of this region, with expected helical tendency for the TAD1 region. As the role of the proline-rich domain is yet not well understood our results can contribute to further successful investigations.