title: Loss of intramolecular electrostatic interactions and limited conformational ensemble may promote self-association of cis-tau peptide.
abstract: Self-association of proteins can be triggered by a change in the distribution of the conformational ensemble. Posttranslational modification, such as phosphorylation, can induce a shift in the ensemble of conformations. In the brain of Alzheimer's disease patients, the formation of intra-cellular neurofibrillary tangles deposition is a result of self-aggregation of hyper-phosphorylated tau protein. Biochemical and NMR studies suggest that the cis peptidyl prolyl conformation of a phosphorylated threonine-proline motif in the tau protein renders tau more prone to aggregation than the trans isomer. However, little is known about the role of peptidyl prolyl cis/trans isomerization in tau aggregation. Here, we show that intra-molecular electrostatic interactions are better formed in the trans isomer. We explore the conformational landscape of the tau segment containing the phosphorylated-Thr(231)-Pro(232) motif using accelerated molecular dynamics and show that intra-molecular electrostatic interactions are coupled to the isomeric state of the peptidyl prolyl bond. Our results suggest that the loss of intra-molecular interactions and the more restricted conformational ensemble of the cis isomer could favor self-aggregation. The results are consistent with experiments, providing valuable complementary atomistic insights and a hypothetical model for isomer specific aggregation of the tau protein.
authors.affiliation: Department of Chemistry and the Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia, 30302-4098.
authors.forename: Arghya
authors.initials: A
authors.lastname: Barman
authors.forename: Donald
authors.initials: D
authors.lastname: Hamelberg
mesh_terms: D006801:Humans; D007536:Isomerism; D056004:Molecular Dynamics Simulation; D066329:Protein Aggregates; D011487:Protein Conformation; D055672:Static Electricity; D013816:Thermodynamics; D016875:tau Proteins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D066329:Protein Aggregates; D016875:tau Proteins
keywords: Tau protein; accelerated molecular dynamics; cis/trans isomerization; conformational sampling; electrostatic interactions; free energy profile; neurofibrillary tangles