4D Non-uniformly sampled HCBCACON and 1 J(NCα)-selective HCBCANCO experiments for the sequential assignment and chemical shift analysis of intrinsically disordered proteins
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A pair of 4D NMR experiments for the backbone assignment of disordered proteins is presented. The experiments exploit 13C direct detection and non-uniform sampling of the indirectly detected dimensions, and provide correlations of the aliphatic proton (Hα, and Hβ) and carbon (Cα, Cβ) resonance frequencies to the protein backbone. Thus, all the chemical shifts regularly used to map the transient secondary structure motifs in the intrinsically disordered proteins (Hα, Cα, Cβ, C′, and N) can be extracted from each spectrum. Compared to the commonly used assignment strategy based on matching the Cα and Cβ chemical shifts, inclusion of the Hα and Hβ provides up to three extra resonance frequencies that decrease the chance of ambiguous assignment. The experiments were successfully applied to the original assignment of a 12.8 kDa intrinsically disordered protein having a high content of proline residues (26 %) in the sequence.
KeywordsIntrinsically disordered proteins Non-uniform sampling 13C detection Chemical shifts Residual secondary structure Prolines assignment
This work was supported by the project "CEITEC - Central European Institute of Technology" from European Regional Development Fund, grant number CZ.1.05/1.1.00/02.0068, (J. N., L. Z., and V. S.) and by the Czech Science Foundation, grant numbers P206/11/0758 (J. N., L. Z., and V. S.). J.H.C. acknowledges the support of a Legacy Heritage personal grant by the Israel Science Foundation. Financial support by the Access to Research Infrastructures activity in the 7th Framework Programme of the EC (Contract 228461, EAST-NMR) for conducting the research is gratefully acknowledged. The project is a part of Joint Research Activity in the 7th Framework program of the EC (BioNMR n. 261863).
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