Recent advances in solid-state nuclear magnetic resonance techniques to quantify biomolecular dynamics.

Abstract

The emergence of solid-state NMR (SSNMR) techniques over the last decade has greatly expanded the range of accessible biomolecules amenable to structural study.1-2 These methods were developed and first applied to a variety of microcrystalline model proteins including BPTI,3 SH3,4-5 ubiquitin,6-7 kaliotoxin,8 and GB1.9-11 These studies demonstrated that individual 13C, 15N and 1H sites throughout the entire protein could be uniquely resolved and assigned for purposes of high-resolution structure determination. Whereas traditional solid-state NMR approaches required site-specific isotopic labeling, the new developments enable entire proteins to be examined by resolving signals in multiple dimensions. These capabilities also permit the measurement of dynamic parameters through correlation spectroscopy, which increases the throughput, sensitivity, reliability and reproducibility of such measurements. A major advantage of SSNMR is that a large range of sample conditions and types can be examined, including many that are not accessible to solution NMR methods, such as membrane proteins and fibrils in addition to microcrystals. Recent examples include fibrils of the HET-s prion,12 high molecular weight oligomers of αB crystallin,13 the tetrameric assembly of the M2 peptide with bound amantadine drug in physiologically relevant bilayers,14 the trimeric membrane protein YadA,15 the photoreceptor proteorhodopsin,16 fibrils of the core domain of transthyretin,17 and beta-amyloid plaques derived from the brains of Alzheimer's disease patients.18 Such studies have opened up new avenues for exploration of fundamental biophysics and biochemistry, and yielded insights into clinically relevant events in membranes and aggregated states not accessible to solution NMR or X-ray crystallography. Moreover, SSNMR experiments are applicable over a larger range of temperatures than can be accessed by solution NMR19 and thereby enable a continuum of experimental conditions from physiological temperatures to the cryogenic temperatures at which most crystal structures are solved. Another advantage of NMR methods in general is that they are non-perturbing and do not require covalent modification of the protein. Thus, the dynamic information procured from such experiments has the potential to accurately represent the native protein behavior. This review focuses on developments over the last five years, regarding methods and applications of dynamics studies by solid-state NMR over timescales ranging from nanoseconds to days.