Abstract
The amount of bonds between constituting parts of a protein aggregate were determined in wild type (WT) and A53T α-synuclein (αS) oligomers, amyloids and in the complex of thymosin-β4–cytoplasmic domain of stabilin-2 (Tβ4-stabilin CTD). A53T αS aggregates have more extensive βsheet contents reflected by constant regions at low potential barriers in difference (to monomers) melting diagrams (MDs). Energies of the intermolecular interactions and of secondary structures bonds, formed during polymerization, fall into the 5.41 kJ mol−1 ≤ Ea ≤ 5.77 kJ mol−1 range for αS aggregates. Monomers lose more mobile hydration water while forming amyloids than oligomers. Part of the strong mobile hydration water–protein bonds break off and these bonding sites of the protein form intermolecular bonds in the aggregates. The new bonds connect the constituting proteins into aggregates. Amyloid–oligomer difference MD showed an overall more homogeneous solvent accessible surface of A53T αS amyloids. From the comparison of the nominal sum of the MDs of the constituting proteins to the measured MD of the Tβ4-stabilin CTD complex, the number of intermolecular bonds connecting constituent proteins into complex is 20(1) H2O/complex. The energies of these bonds are in the 5.40(3) kJ mol−1 ≤ Ea ≤ 5.70(5) kJ mol−1 range.
Highlights
One of the main reasons intrinsically disordered proteins (IDPs) are so important in different physiological processes is that they are capable of forming a bewildering variety of interactions
Untagged versions of α-synuclein variants were expressed in E. coli cells and Briefly, untagged versions of α-synuclein variants were expressed in E. coli cells and purified using anion exchange chromatography, while stabilin C-terminal domain (CTD) was expressed with purified using anion exchange chromatography, while stabilin CTD was expressed with an N-terminal His-tag and purified on a Ni-NTA affinity column
Melting diagrams (MDs) are the relative give the amounts of the mobile hydration water
Summary
One of the main reasons intrinsically disordered proteins (IDPs) are so important in different physiological processes is that they are capable of forming a bewildering variety of interactions. They can undergo induced folding or unfolding, they are able to form physiological or pathological aggregates, and even form fuzzy complexes, where disorder is retained during the interaction [1]. Detailed structural and preparation information can be found in [2,3]. The other system consists of two proteins—thymosin-β4 (Tβ4 ) and cytoplasmic domain of stabilin-2 (stabilin CTD)—which form a 1:1 complex (see [4,5] for structural information and for details of preparation)
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