The Residual Structure of Unfolded Proteins was Elucidated from the Standard Deviation of NMR Intensity Differences

Introduction: Sensitive methods are necessary to identify the residual structure in an unfolded protein, which may be similar to the functionally native structure. Signal intensity in NMR experiments is useful for analyzing the line width for a dynamic structure; however, another contribution is contained. Methods: Here, the signal-intensity difference along the sequence was used for probability to calculate the standard deviation. Results: The relative values of the standard deviations were 0.57, 0.57, and 0.66 for alpha-synuclein wild-type, A53T, and A30P, respectively. This revealed that the flexible region was mainly in the Cterminal region of alpha-synuclein at higher temperatures as observed by the amide-proton exchange studies. Conclusion: In particular, the flexible structure was induced by the A30P mutation.