Intermediate filaments (IF) are intracellular structures which can assemble from a single polypeptide, through a series of several distinct interactions, into complex fibers. Models of IF structure and assembly have proliferated, but studies of large IF fragments (head, coiled coil rod, and tail) have been unable to clarify the later steps of assembly, or the structure of the full length filament. The goal of this proposed work is to characterize smaller fragments of an IF, vimentin, each capable of a subset of the specific interactions postulated to occur in the larger fiber. Knowledge of the relative orientations and registers of these components, along with their oligomeric state, will allow discernment between proposed assembly models, yielding insight into the structural basis of certain skin, muscle, and neuronal diseases. Fragments will initially be studied by CD, FTIR, and NMR spectroscopy, and by analytical ultracentrifugation. Crystallization of well-ordered complexes will be attempted in order to solve high resolution structures. To date, there is no such structural information on any component of any IF. This data will specify the organization of components within IF fibers; it will also provide information useful for both the prediction and design of complex coiled coil structures.
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