Protein NMR spectroscopy: folded vs. unfolded protein

Figure showing the relationship between the 2D 1H-15N HSQC spectra of folded and unfolded proteins. The signal dispersion in the proton dimension is significantly diminished for unfolded proteins. Note that alpha-helix-rich proteins also exhibit low signal dispersion in the proton dimension; however, the example protein here contains mosts beta-strands, and therefore shows many signals &gt; 8.5 ppm.<br>The NMR spectra are of the same protein with the amino acid sequence indicated on the top. In the middle, left, the 2D 1H-15N HSQC spectrum of a folded 2x10 kDa dimer. On the right, the HSQC spectrum of the unfolded monomer. In both cases, the resonance from S156 is circled, with its position in the amino acid sequence indicated. On the bottom is the PDB file 4mjh depicting the structure of the folded dimer. On the bottom right is a structural model of an intrinsically disordered protein shown as an example. This was taken from the Protein Ensemble Database PED1AAD, with the number of residues trimmed to equal that of the folded structure (PDB 4mjh).