Comparison of backbone modification in protein β-sheets by α→γ residue replacement and α-residue methylation.

The mimicry of protein tertiary structure by oligomers with unnatural backbones is a significant contemporary research challenge. Among common elements of secondary structure found in natural proteins, sheets have proven the most difficult to address. Here, we report the systematic comparison of different strategies for peptide backbone modification in β-sheets with the goal of identifying the best method for replacing a multi-stranded sheet in a protein tertiary fold. The most effective sheet modifications examined led to native-like tertiary folding behavior with a thermodynamic folded stability comparable to the prototype protein on which the modified backbones are based.