Abstract
Study of model β‐hairpin peptides allows for better understanding of the factors involved in the formation of β‐sheet secondary structure in proteins. It is known that turn sequence, sidechain–sidechain interactions, interstrand hydrogen bonding, and β‐sheet propensity of residues are all important for β‐hairpin stability in aqueous solution. However, interactions of the sidechains of the terminal residues of hairpins are thought to contribute little to overall hairpin stability since these residues are typically frayed. Here, the authors report a stabilizing hydrophobic cluster of residues at the termini of the naturally occurring excised N‐terminal β‐hairpin of Ubiquitin that folds autonomously in aqueous solution. Our data show that deletion of Met1 and Val17 from this hairpin destabilized the folded state in both aqueous solution and in aqueous‐methanol solutions. These results suggest that interactions of terminal residues which are usually frayed can nonetheless contribute significantly to overall stability of β‐hairpin. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 394–398, 2008.
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