Investigation of the effect of point mutations on human transthyretin protein structure and aggregation

In cell proteins will be synthesized away the nascent chain to folded state. For almost all proteins, based on appropriate conditions, there would be an aggregated state, generally called amyloid can lead to neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases. Generally, aggregations causing these pathological conditions are initiated from intrinsic disorders (e.g., mutations). Transthyretin, a tetrameric transporter protein that in its monomeric form can self-associate to shape amyloid-beta aggregation is one of these proteins. All the point-mutations that can expose buried hydrophobic region, unstable tetrameric formation, and ultimately cause aggregation can lead to pathological conditions such as Transthyretin amyloidosis disorders or transthyretin amyloid cardiomyopathy (TAC). This study focuses on producing andisolating recombinant human transthyretin in E.Coli by making specific amino acid alternation via site-directed mutagenesis. To evaluate protein structure and aggregation, some techniques such as turbidity, mass spectrometry, dynamic light scattering (DLS), fluorescence, circular dichroism (CD), and X-ray crystallography have been widely used. Results show that a W۴۱F protein mutation in transthyretin leads to intense instability and amyloid fibril accelerated formation. In contrast, W۷۹F protein mutation shows nosensible structure or stability alternation. Changes in protein sequence and structure can affect properties such as hydrophobicity, secondary structure propensity, and charge. These changes in the way of increasing the hydrophobicity or polypeptide propensity to convert from alpha-helix to beta-sheet and decreasing the total surface net charge of protein can increase the aggregation propensity.

کلیدواژه ها:

Amyloid-β ، Protein folding ، Neurodegenerative diseases ، Transthyretin ، Intrinsic disorders