UC Davis

Intermediate filament (IF) proteins self-assemble into coiled-coil structures via a central rod domain. Disordered head or tail domains of low complexity flank this region and are required for assembly into unit length filament bundles of eight or more coiled-coil tetramers that anneal end to end to make fully formed filaments. These disordered regions can be responsible for many cellular regulation processes and are implicated in numerous diseases that are associated with mutations in these regions. However, it is difficult to characterize these disordered regions in the context of whole protein and assemblies using high resolution techniques such as crystallography and solution state nuclear magnetic resonance (NMR). To pursue a high-resolution structure of an IF protein, solid state NMR is used to address the limitations of many low-resolution techniques and other high-resolution techniques that are incompatible with large or disordered proteins. The head and tail domains in full-length vimentin and the tail domain fibrils of atypical isoform of tropomyosin Tm1 I/C are investigated using CC DARR, NCACX and NCOCX NMR experiments with isotopic labeling techniques such as paramagnetic relaxation enhancement, segmental labeling, 50:50 mixed labeling and glycerol labeling. The distance restraints from these experiments will contribute to a calculation of a high-resolution structure. Understanding details of the structure of the disordered domains in the tail domain polymers and fully assembled filaments can give insight to the assembly mechanism and function of other intermediate filament proteins.