Accurate measurement of 3JHNHα couplings in small or disordered proteins from WATERGATE-optimized TROSY spectra
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Provided that care is taken in adjusting the WATERGATE element of a 1H–15N TROSY-HSQC experiment, such that neither the water magnetization nor the 1Hα protons are inverted by its final 180° pulse, 3JHNHα couplings can be measured directly from splittings in the 1H dimension of the spectrum. With band-selective 1H decoupling, very high 15N resolution can be achieved. A complete set of 3JHNHα values, ranging from 3.4 to 10.1 Hz was measured for the 56-residue third domain of IgG-binding protein G (GB3). Using the H–N–Cα–Hα dihedral angles extracted from a RDC-refined structure of GB3, 3JHNHα values predicted by a previously parameterized Karplus equation agree to within a root-mean-square deviation (rmsd) of 0.37 Hz with the experimental data. Values measured for the Alzheimer’s implicated Aβ1−40 peptide fit to within an rmsd of 0.45 Hz to random coil 3JHNHα values.
KeywordsAbeta IDP Karplus curve Random coil Synuclein Protein NMR
We thank Dennis A. Torchia for useful discussions, and Jung Ho Lee for preparing the sample used for Fig. 4c. This work was supported by the Intramural Research Program of the National Institute of Diabetes and Digestive and Kidney Diseases and the Intramural Antiviral Target Program of the Office of the Director, NIH.
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