NMR spin relaxation approaches for characterizing protein motions

Flexibilities in protein conformations are essential for their functions, playing key roles in molecular recognition, ratelimiting conformational transitions, and catalysis. Information on the structure of proteins should be complemented by the information on their motion, both to characterize the protein and to understand its function. The relationship between protein structure, dynamics, and function is very challenging to study because the conformational space available to a protein is extensive and the time scales of conformational motions range widely, from picoseconds to seconds. These time scales are accessible by solution NMR making it a suitable technique for investigating the motions in proteins. In this review, an introduction to NMR spin relaxation approaches is provided to investigate protein dynamics on picosecondto- second time scales, showing the recent NMR techniques as well as case studies on protein motions. The importance of dynamic features of proteins for their molecular recognition processes and the catalytic activities of enzymes is demonstrated using spin relaxation approaches, showing that solution NMR spectroscopy is a unique tool for studying protein dynamics.