Solution structure and dynamics of integral membrane proteins by NMR: a case study involving the enzyme PagP

Solution NMR spectroscopy is rapidly becoming an important technique for the study of membrane protein structure and dynamics. NMR experiments on large perdeuterated proteins typically exploit the favorable relaxation properties of backbone amide (15)N-(1)H groups to obtain sequence-specific chemical shift assignments, structural restraints, and a wide range of dynamics information. These methods have proven successful in the study of the outer membrane enzyme, PagP, not only for obtaining the global fold of the protein but also for characterizing in detail the conformational fluctuations that are critical to its activity. NMR methods can also be extended to take advantage of slowly relaxing methyl groups, providing additional probes of structure and dynamics at side chain positions. The current work on PagP demonstrates how solution NMR can provide a unique atomic resolution description of the dynamic processes that are key to the function of many membrane protein systems.