アイテム詳細

要旨

Various processes in the living cell are regulated by very large protein machineries with molecular weights in the megadalton regime. However, structural investigations of these large systems by solution-state NMR are challenging due to their slow rotational diffusion. Here we describe an approach, which opens new perspectives in the investigation of soluble supramolecular modules by magic-angle spinning (MAS) NMR. The absence of rotational diffusion in MAS-induced protein sediments allows typical solid-state NMR techniques without the need of invasive precipitation or crystallization procedures. The combination with protein deuteration, proton-detection and paramagnetic relaxation enhancement enabled us to observe and to assign backbone amide resonances of a 20S proteasome assembly with a molecular weight of 1.1 MDa. Similarly, we used the approach to characterize the polydisperse and highly dynamic small heat-shock protein αB-crystallin (600 kDa) with respect to its copper-dependent chaperone activity and its mechanism of binding destabilized substrate proteins.