Bulky Dehydroamino Acids Enhance Proteolytic Stability and Folding in β-Hairpin Peptides

Abstract

The bulky dehydroamino acids dehydrovaline (ΔVal) and dehydroethylnorvaline (ΔEnv) can be inserted into the turn regions of β-hairpin peptides without altering their secondary structures. These residues increase proteolytic stability, with ΔVal at the (i + 1) position having the most substantial impact. Additionally, a bulky dehydroamino acid can be paired with a D-amino acid (i.e., D-Pro) to synergistically enhance resistance to proteolysis. A link between proteolytic stability and peptide structure is established by the finding that a stabilized ΔVal-containing β-hairpin is more highly folded than its Asn-containing congener.

Impact of Bulky Dehydroamino Acids on the Structure and Proteolytic Stability of Peptides

“…2.5 times longer than that of the control peptide. [10] Thus, we established that a Damino acid and a bulky ∆AA can synergistically increase the stability of a β-hairpin to proteolysis without disrupting its secondary structure.…”

“…We were pleased to discover that replacing the (i + 1) Asn residue with a bulky ∆AA led to a substantial increase in proteolytic stability, as both ∆ValG and ∆EnvG exhibited half-lives that were six-to sevenfold longer than the half-life of NG (Figure 4). [10] This exciting result caused us to wonder if the beneficial impact of bulky ∆AAs was confined to the (i + 1) position, or if insertion of ∆Val or ∆Env at the (i + 2) position would also protect β-hairpins from proteolysis. Accordingly, two other variants of NG in which the Gly residue is replaced by a bulky ∆AA (N∆Val and N∆Env) were synthesized and evaluated in the proteolysis assay.…”

“…threefold increase in half-life was not as dramatic as the effect seen with bulky ∆AAs at the (i + 1) position. [10] Nonetheless, this measurable improvement in proteolytic stability was substantial enough to justify the preparation of β-hairpins pairing a stabilizing D-Pro residue at (i + 1) with a bulky ∆AA at (i + 2) (p∆Val and p∆Env). Each of these peptides adopted a β-hairpin structure as evidenced by NMR spectroscopy.…”

A general method for preparation of N‐Boc‐protected or N‐Fmoc‐protected α,β‐didehydropeptide building blocks and their use in the solid‐phase peptide synthesis

“…Recently, it has been found that peptides with α,β‐didehydro‐α‐amino acid residues can form hydrogels and may be used as a platform for drug delivery which make these residues important for medicinal chemistry. The significant quality of α,β‐didehydro‐α‐amino acid residues, from the biological point of view, is increasing the resistance of peptides to enzymatic hydrolysis . Recently, Castle and coworkers have shown that ΔVal can stabilise β‐hairpin peptides to proteolysis .…”

“…[11][12][13] Recently, Castle and coworkers have shown that ΔVal can stabilise β-hairpin peptides to proteolysis. 13 α,β-Didehydro-α-amino acids play a main role in biosynthetic pathways of some natural products, especially lantibiotics where the ΔAla or ΔAbu residues are involved in lanthionine formation. 14,15 Another class of compounds containing α,β-didehydro-α-amino acid residues, being intensively studied recently, is thiopeptide antibiotics.…”