engleski

Probing Protein Stability with Non-natural Amino Acids

Quantitative replacement of methionine with its non-natural amino acid analogues, norleucine, selenomethionine and telluro-methionine in human recombinant annexin V, is applied to study conformational and folding properties in solution. This procedure replaces each methionine sulphur atom with Se, Te or -CH2-, providing single-atom exchanges, or >>atomic mutations<<. Using guanidine chloride as denaturant, the estimated stabilities of protein variants are not significantly changed. The denaturation midpoints are shifted towards lower values owing to the increase in the hydrophobicity of exchanged residues. Co-operativity expressed in terms of m-values is also affected by such exchanges and is highly correlated with the physical properties of methionine and its analogues in solution. This approach can contribute to a detailed understanding of interactions of particular amino acids and their implications on protein folding and protein-ligand interactions.

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