| A growing number of studies have reported that liquid-liquid phase separation(LLPS)of intrinsically disordered proteins(IDPs)is closely related to a variety of diseases including neurodegenerative diseases and cancer.Understanding the mechanisms of LLPS and aggregation,and the relationship between the two status can lead us a new path to understand these diseases and look for cures.This thesis focuses on the study of LLPS and aggregation mechanisms of disordered sequences of intrinsically disordered proteins in vitro.For the disordered sequences of two different types of prion-like region(PLD)and low complexity sequence(LCD),the disordered regions in RBM14 protein and U1-70K protein were selected as research objects.In this thesis,the mechanisms for their self-assembly in vitro are presented respectively.It was found that the PLD sequence R(284-572)of RBM14 containing Y[G/N/A/S]AQ or[S/G]YG repeat motifs has a strong tendency to aggregate and can spontaneously undergo LLPS in a non-crowded environment.It is highly probable that the aggregates are rich in ?-sheet structures.The main forces driving the aggregation may be hydrophobic interactions and conjugate-conjugate interactions,where the phenolic hydroxyl groups provided by tyrosine may be the main driving force source.For the protein U1-70K,this study found a new pattern of LLPS induced by cross-positive and negative charge repeats.Specifically,the amino acid composition of LC1 is relatively simple,and the main driving force of LLPS is electrostatic interaction.The diversity of residues in LC2 grants it more diverse interactions,potentially including hydrophobic effect and interactions with counteranions.In both cases,cations in the domains contributed more interactions during the LLPS.These findings of the LLPS behavior of U1-70K LC domain and the mechanism will shed substantial light on further researches on relationships between U1-70K and Alzheimer's disease. |
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