Measurement of backbone hydrogen-deuterium exchange in the type III secretion system needle protein PrgI by solid-state NMR

[Display omitted] •We apply the RelaX-EXSY method to measure H/D exchange in a solid state protein.•The method requires proton detection and performs better at higher external magnetic fields.•Amide exchange rates are measured in deuterated Salmonella typhimurium type iii secretion system (T3SS) needles. In this report we present site-specific measurements of amide hydrogen-deuterium exchange rates in a protein in the solid state phase by MAS NMR. Employing perdeuteration, proton detection and a high external magnetic field we could adopt the highly efficient Relax-EXSY protocol previously developed for liquid state NMR. According to this method, we measured the contribution of hydrogen exchange on apparent 15N longitudinal relaxation rates in samples with differing D2O buffer content. Differences in the apparent T1 times allowed us to derive exchange rates for multiple residues in the type III secretion system needle protein.