NMR characterization of the full-length recombinant murine prion protein, mPrP(23-231).

The recombinant murine prion protein, mPrP(23-231), was expressed in E. coli with uniform 15N-labeling. NMR experiments showed that the previously determined globular three-dimensional structure of the C-terminal domain mPrP(121-231) is preserved in the intact protein, and that the N-terminal polypeptide segment 23-120 is flexibly disordered. This structural information is based on nearly complete sequence-specific assignments for the backbone amide nitrogens, amide protons and alpha-protols of the polypeptide segment of residues 121-231 in mPrP(23-231). Coincidence of corresponding sequential and medium-range nuclear Overhauser effects (NOE) showed that the helical secondary structures previously identified in mPrP(121-231) are also present in mPrP(23-231), and near-identity of corresponding amide nitrogen and amide proton chemical shifts indicates that the three-dimensional fold of mPrP(121-231) is also preserved in the intact protein. The linewidths in heteronuclear 1H-15N correlation spectra and 15N[1H]-NOEs showed that the well structured residues 126-230 have correlation times of several nanoseconds, as is typical for small globular proteins, whereas correlation times shorter than 1 nanosecond were observed for all residues of mPrP(23-231) outside of this domain.