Study of protein folding and misfolding by NMR spectroscopy

National Institute Of Diabetes And Digestive And Kidney Diseases

Investigators

Linked publications & trials

Abstract

In close collaboration with Philip Anfinrud, novel hardware was designed and developed that makes it possible, for the first time, to obtain demonstrate that it is readily possible to monitor the folding of the protein chain in a residue-specific manner upon jumping the applied pressure. Pressure changes of up to 2.5 kbar, requiring 1-2 ms, are shown to feasible and compatible with the recording of high quality NMR data. Experiments have been demonstrated for a pressure-sensitized mutant of the protein ubiquitin, whose folding previously has been studied extensively by other methods. The appearance of the native, folded ubiquitin NMR spectrum shows the same time dependence for all its residues and is found to be quite slow. Remarkably, however, the disappearance of the unfolded NMR resonances is more than an order of magnitude faster and shows a large dispersion in rates, reflecting the transitioning of individual residues from full disorder into a partially ordered but not yet fully folded protein state. 15N relaxation rates measured during the folding process are consistent with the rates at which residues disappear from the unfolded NMR spectrum after switching to low pressure and are indicative of motions on a micro-second time scale.