Using 1HN amide temperature coefficients to define intrinsically disordered regions: An alternative NMR method

Abstract

This report describes a cost-effective experimental method for determining an intrinsically disordered protein (IDP) region in a given protein sample. In this area, the most popular (and conventional) means is using the amide (1HN) NMR signal chemical shift distributed in the range of 7.5–8.5 ppm. For this study, we applied an additional step: analysis of 1HN chemical shift temperature coefficients (1HN-CSTCs) of the signals. We measured 1H–15N two-dimensional NMR spectra of model IDP samples and ordered samples at four temperatures (288, 293, 298, and 303 K). We derived the 1HN-CSTC threshold deviation, which gives the best correlation of ordered and disordered regions among the proteins examined (below −3.6 ppb/K). By combining these criteria with the newly optimized chemical shift range (7.8–8.5 ppm), the ratios of both true positive and true negative were improved by approximately 19% (62–81%) compared with the conventional “chemical shift-only” method.