Quences (Supplementary Figure 4e, Supplementary Figure 5a , and 6 and Supplementary Data five). Previously published resolution NMR data have shown that the PGGG sequences in tau can adopt kind II -turns7, plus the 301PGGG304 sequence preceding 306VQIVYK311 is compatible with the formation of a -hairpin. We illustrated the R2R3 306VQIVYK311-containing fragment Aggrecan Inhibitors MedChemExpress derived from low energy expanded models made by every process (Supplementary Figure 4c, d). The 306VQIVYK311-containing interface has the highest frequency of disease-associated mutations, specifically P301L and P301S (Fig. 1a). Other prospective amyloid-forming regions, which include the aggregation-prone 275VQIINK280 (Supplementary Figure six), can also be preceded by 271PGGG274 and predicted to kind a -hairpin (Supplementary Figure 4e and Supplementary Figure five), nevertheless, it can be absent in current cryo-EM structures of tau aggregates3,43. Mapping known missense mutations onto the ab initio -hairpin structure in the R2R3 interface (Supplementary Figure 4f), we hypothesized that this cluster of disease-associated mutations could destabilize the -hairpin secondary structure, as a result exposing the amyloid motif 306VQIVYK311 and enabling aggregation. This model is compatible with current cryo-EM findings that indicate a disengagement from the 306VQIVYK311 N-terminal flanking sequence within a fibril structure3. Therefore, we focused our studies on the R2R3 motif of tau that includes 306VQIVYK311. P301L promotes extended forms of tau. In silico modeling corroborated recent biochemical findings16 and recommended a minimal sequence necessary to form a collapsed structure about 306VQIVYK311. To know how these structures could self-assemble, we employed molecular dynamics (MD) simulations of two tau SC66 Cancer peptide fragments comprising the minimally structured fragment centered about the R2R3 interface (295DNIKHVPGGGSVQIVYK311): R2R3-WT and R2R3-P301L (Supplementary Table 2). To enable adequate sampling of oligomer structures, we employed an unbiased algorithm based on a lately developed symmetry-constraint approach44. The trimer conformations obtained in simulations are depicted on a root imply square deviation (RMSD) matrix for each the R2R3-WT (Fig. 3a) and also the R2R3-P301L mutant peptide fragments (Fig. 3b). For the R2R3-WT peptide fragment, we observe a dominant population of trimeric conformations composed of hairpins, whereas the P301L disease-associated mutation stabilizes an extended fibrillar kind. The power basin for the R2R3-WT peptide fragment is predicted to become 5 kJmol lower inside a collapsed state than an extended state, whereas the R2R3-P301L peptide fragment is 3 kJmol reduce in an extended state than a collapsed state (Fig. 3c and Supplementary Information 6). Moreover, the free-energy surface suggests an energy barrier of 5 kJmolaRMSD matrix for wild sort 9 8 7 six Time (s) 5 four 3 two 1 0b9 8 7 6 Time (s) five four three 2 1 0 1 2 0.7 RMSD (nm) 3 4 5 Time (s) 6 7 three.8 eight 9 0 1 2 0.7 three 4 5 Time (s) RMSD (nm) 6 7 3.five 8 9 RMSD matrix for P301L mutantc9 8CollapsedWild variety P301LExtendedFree energy (kJmol)6 5 four 3 2 1 0 0 0.2 0.four 0.6 0.8 1 RMSD from hairpin (nm)Fig. 3 Wild-type and mutant peptides differentially populate collapsed and extended conformations. a Trimer conformations obtained from MD simulations of WT peptide fragment (R2R3-WT) together with the sequence 295DNIKHVPGGGSVQIVYK311. Two-dimensional root mean-squared-differences (RMSD’s) are calculated in between all pairs of conformations visited for the duration of MD simulations. Snapshots of trim.
