, Volume 47, Issue 3, pp 171-181
Date: 01 May 2010

HA-detected experiments for the backbone assignment of intrinsically disordered proteins

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Abstract

We propose a new alpha proton detection based approach for the sequential assignment of natively unfolded proteins. The proposed protocol superimposes on following features: HA-detection (1) enables assignment of natively unfolded proteins at any pH, i.e., it is not sensitive to rapid chemical exchange undergoing in natively unfolded proteins even at moderately high pH. (2) It allows straightforward assignment of proline-rich polypeptides without additional proline-customized experiments. (3) It offers more streamlined and less ambiguous assignment based on solely intraresidual 15N(i)-13C′(i)-Hα(i) (or 15N(i)-13Cα(i)-Hα(i)) and sequential 15N(i + 1)-13C′(i)-Hα(i) (or 15N(i + 1)-13Cα(i)-Hα(i)) correlation experiments together with efficient use of chemical shifts of 15N and 13C′ nuclei, which show smaller dependence on residue type. We have tested the proposed protocol on two proteins, small globular 56-residue GB1, and highly disordered, proline-rich 47-residue fifth repeat of EspFU. Using the proposed approach, we were able to assign 90% of 1Hα, 13Cα, 13C′, 15N chemical shifts in EspFU. We reckon that the HA-detection based strategy will be very useful in the assignment of natively unfolded proline-rich proteins or polypeptide chains.