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Bicyclic peptides as type I/type II beta-turn scaffolds
A Lombardi1, G D'Auria, M Saviano
1Centro Interdipartimentale di Ricerca sui Peptidi Bioattivi CEINGE--Biotecnologie Avanzate, Napoli, Italy.
Biopolymers
|January 1, 1996
Summary
This study reveals that the rigid bicyclic scaffold of a neurokinin A antagonist can form both type I and type II beta-turns. This structural flexibility is independent of the specific amino acid sequence at key positions.
Area of Science:
- Medicinal Chemistry
- Structural Biology
- Peptide Design
Background:
- A potent bicyclic peptide neurokinin A antagonist, cyclo(Met1-Asp2-Trp3-Phe4-Dap5-Leu6)cyclo(2 beta-5 beta), was previously designed and synthesized.
- This antagonist features distinct type I and type II beta-turns stabilized by its bicyclic structure.
Purpose of the Study:
- To investigate whether the observed beta-turn structures are dictated by the bicyclic scaffold or the amino acid residues.
- To synthesize and structurally characterize a pseudo-symmetrical analogue to probe the role of amino acid composition.
Main Methods:
- Synthesis of a pseudo-symmetrical analogue: cyclo(Phe1-Asp2-Trp3-Phe4-Dap5-Trp6)cyclo(2 beta-5 beta).
- Structural characterization using techniques applicable to both crystal states and solution.
Main Results:
- Experimental evidence confirms the bicyclic structure acts as a rigid scaffold.
- The scaffold supports the formation of both type I and type II beta-turns.
- Beta-turn formation is independent of the specific amino acid composition at the turn positions.
Conclusions:
- The rigid bicyclic scaffold is the primary determinant of beta-turn formation.
- This scaffold offers a versatile platform for designing peptide antagonists with controlled secondary structures.
- Findings advance the understanding of peptide structure-function relationships for neurokinin A antagonists.