NMR Studies of Polypeptide Structuring and Aggregation
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The importance of studying polypeptide structuring and folding mechanisms lies in the damage caused by misfolding proteins in the human body. The misfolding of proteins can lead to the off-pathway formation of aggreagates that can prove harmful to living cells. Several disease states result from this aggregation process, e.g. Parkinson's disease in which &alpha-synuclein is accumulated into Lewy bodies within the brain. In this work, the aggregation process of &alpha-synuclein is examined through the use of NMR, primarily <super>15</super>N-NMR. Aromatic-containing, well-folded &beta-hairpins have been shown to be effective at interfering with the fibril formation pathway. Through NMR, the binding of these hairpins to &alpha-synuclein and the divertion of the fibrils to a non-amyloid precipitate is explored. The design of stable protein-like structures allows for the study of specific interactions which contribute to folding. The trunctation and mutation of a poorly folded 39-residue peptide has produced 20-residue constructs that are > 95% folded in water. These constructs have been designated as the `Trp-cage' motif. This construct is characterised by an N-terminal &alpha-helix and hydrophobic collapse centred on a tryptophan indole ring. The majority of this work explores essential features of the Trp-cage that are responsible for its stability. The later part focuses on the circular permutation of the Trp-cage, followed by the cyclisation of the most stable motif. This results in a hyperstable Trp-cage (T<sub>M</sub> >> 100° C at pH 7) which possesses the same diagnostic features as the standard Trp-cage structure.
- Chemistry