Dynamic properties of proteins are essential for their function. NMR can reveal protein dynamics in solution on a broad range of timescales and at atomic resolution. However, NMR studies of large proteins remain challenging since conventional NMR methods are constrained to small proteins. The aim of this project is to extend the NMR size limit to large protein complexes by combining recent developments in site-specific labeling schemes with novel NMR methods employing state-of-the-art spectrometers. This will facilitate the study of functionally essential but so far uncharacterized dynamics and substrate interactions of two large protein complexes, providing unprecedented insight into the relationship between dynamics, structure and function. Since most proteins are dynamic, extending the scope of protein complexes that are amenable to NMR study is of great interest to many areas of molecular biology. Studies will be conducted on the eukaryotic exosome, a 370 kDa soluble, asymmetric decamer involved in RNA degradation and processing, and the 80 kDa Na+/H+ antiporter NapA, an integral membrane dimer involved in ion transport. For the exosome, individual subunits will be 13C-methyl labeled; the employment of sophisticated NMR methods will then permit the detection of functionally essential dynamics and RNA-substrate binding patterns of the exosome. As NapA is a low-yield membrane protein, an inexpensive 19F-labeling approach will be employed to reveal global transport dynamics and local gating motions. Exosome production and all NMR experiments are to be conducted in Remco Spranger’s lab at the University of Regensburg, Germany. NapA will be produced during a secondment in David Drew’s lab at Stockholm University, Sweden.