Transthyretin and Amyloidosis: Probing the Role of Conformational Flexibility and Transient States by Solution NMR Spectroscopy
IR@IICB: CSIR-Indian Institute of Chemical Biology, Kolkata
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| Title |
Transthyretin and Amyloidosis: Probing the Role of Conformational Flexibility and Transient States
by Solution NMR Spectroscopy
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| Creator |
Das, Jitendra K
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| Subject |
Structural Biology & Bioinformatics
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| Description |
Abstract: Extracellular deposition of self-assembled insoluble fibrils formed from soluble proteins like transthyretin (TTR) causes amyloidosis leading to organ dysfunction. Destabilizing mutations in TTR induce conformational changes in the native structure leading to tetramer dissociation and formation of partially unfolded intermediates. The significance of these conformational changes caused by the amyloidogenic mutations is not well understood as the amyloidogenic propensity cannot be explained by the gross structural differences. With negligible structural differences among pathogenic and stable variants, their pathogenicity might be scripted by their conformational flexibility.
In this work, a correlation has been demonstrated between the conformational flexibility concomitant with the formation of non-native intermediates with the pathogenic propensity of TTR using NMR spectroscopy. Quantifying the backbone dynamics over an extended timescale revealed that the solvent exposed regions of TTR exhibit higher flexibility at picosecond-nanosecond timescale in comparison to the residues at the β-sheets of the central core. In contrast to fast motions, conformational fluctuations at slower (~millisecond) timescale are almost exclusively located in the β-sheets forming the hydrophobic core of the tetramer. The slower motions collectively modulate a conformational excursion event between the native and transiently formed, non-native intermediate states. Using the advantage of NMR spectroscopy in characterizing these transient states, disease causing mutants like V30M and L55P were found to have higher population of transient states with lower free energy and faster kinetics of conversion than the wild-type and the protective mutant (T119M) and may explain their higher propensity to form fibrils.
Investigating the temperature dependence of backbone motions, the fast motions were found to exhibit subtle deviation with temperature. The free energy differences from the slow timescale motions were fitted to extract the contribution of enthalpy and entropy towards free energy as well as the change in heat capacity (ΔCP). The variability and extent of ΔCP indicates new structural re-arrangements rather than pure unfolding in the non-native states. These findings basically raise the question if the initial, non-native states are partially unfolded in nature in all pathogenic mutants or how crucial it is to be unfolded to undergo fibrillization.
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| Date |
2017
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| Type |
Thesis
NonPeerReviewed |
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| Format |
application/pdf
application/pdf |
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| Identifier |
http://www.eprints.iicb.res.in/2729/1/Abstract.pdf
http://www.eprints.iicb.res.in/2729/2/Thesis.pdf Das, Jitendra K (2017) Transthyretin and Amyloidosis: Probing the Role of Conformational Flexibility and Transient States by Solution NMR Spectroscopy. PhD thesis, University of Calcutta. |
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| Relation |
http://www.eprints.iicb.res.in/2729/
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