X-Ray Digital Aggregated Dynamics of Intrinsically Disordered Proteins

Abstract

Parkinson's Disease (PD) and Alzheimer Disease (AD) is one of the neurodegenerative pathology. These diseases are occurred by anomalous aggregations of causative proteins.Alpha-synuclein (Syn) is PD's causative proteins and Tau is AD's ones. But these protein's aggregation process haven’t been clear. Additionally, these proteins are one of the famous intrinsically disorder proteins (IDP). Until now, it is difficult to understand aggregation process from static structural information of IDP. Therefore, in this study, we observed that characteristic of single molecule structural fluctuations which occurred anomalous aggregation. Furthermore, we observed dynamical digital aggregation process (from monomer to dimer or trimer). In order to understand single molecular dynamics which occurred aggregation, we measured single molecule structural fluctuations of Syn's wild type (WT) and mutants (E46K, A53T). And, we observed digital aggregations of Tau proteins for the purpose of detecting dynamical process. At these experiments, we used Diffracted X-ray Tracking (DXT). In order to measure movements of the specific binding sites of proteins, DXT monitor X-ray diffraction spots from labeled gold nanocrystal. DXT experiments used the energy of quasi-white x-rays (energy peak-width of 2%, 10-20 keV, BL40XU, SPring-8), for that reason DXT has high time-resolution (0.1ms/frame) and high super-precision (0.1nm scale). As a result from Syn's DXT data, The motion's histograms in WT has simple single Gaussian distribution. However, these in other Syn's mutants which occurred anomalous aggregation have two Gaussian distributions. From DXT results, we confirmed that mutant's structural fluctuation is more rigid than that of WT. In the other hand, Tau dimer is very more flexible than that of monomer and trimer. The motion histograms show that there are very different process between dimerization and trimerization in the digital aggregation observations of Tau proteins.