DISTANCE MEASUREMENTS OF FIBROUS PRION PROTEINS BY PULSE ESR SPECTROSCOPY

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This research was performed to clarify the mechanism of formation of the prion filaments. The structure of prion monomer consists of a tertiary C-terminal domain (three alpha-helices, H1, H2 and H3) and an N-terminal random domain. In the experiments, recombinant prion protein with a cysteine mutation was created by E. Coli expression system and the cysteine residue was labeled by nitroxide spin probe. After aggregated prion filaments induced by detergent, the spin-spin interaction was measured by X-band continuous-wave (CW) electron spin resonance (ESR) or Q-band pulse ESR spectrometer. The inter-spin distance was determined by Monte Carlo fitting for electron-electron interaction signals. The inter-spin distance of prion filaments spin-labeled at H1 or H2 is shorter than that of H3. However, the inter-spin distance of N-terminal domain was not estimated because of polydispersity in distance. These data suggested that H1 and H2 were involved in formation of prion filaments.