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Updated: Jan 25, 2026

Constructing Cyclic Peptides Using an On-Tether Sulfonium Center

Constructing Cyclic Peptides Using an On-Tether Sulfonium Center

Published on: September 28, 2022

Crystal Structures of Protein-Bound Cyclic Peptides.

Alpeshkumar K Malde¹, Timothy A Hill¹, Abishek Iyer^1,2

¹Division of Chemistry and Structural Biology, Institute for Molecular Bioscience , The University of Queensland , Brisbane , Queensland 4072 , Australia.

Chemical Reviews

|May 4, 2019

Summary

Cyclic peptides, unlike small molecules, bind proteins using both main chains and side chains, forming polar contacts and hydrogen bonds. This allows them to modulate protein interfaces more effectively, enhancing affinity and biological activity.

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Area of Science:

Biochemistry and Structural Biology
Medicinal Chemistry
Protein-Protein Interactions

Background:

Cyclization is a key post-translational modification enhancing peptide properties like stability and bioavailability.
Cyclic peptides can incorporate unnatural amino acids and non-peptidic constraints for structural fine-tuning.
Protein binding can further alter cyclic peptide structures in biological environments.

Purpose of the Study:

To analyze the three-dimensional crystal structures of 211 bioactive cyclic peptides bound to 65 proteins.
To investigate bonding modes, backbone and side-chain structures, and the role of polarity, hydrogen bonds, hydrophobic effects, and water in protein interactions.
To compare the binding strategies of cyclic peptides with those of small-molecule drugs.

Main Methods:

Analysis of 211 protein-bound cyclic peptide crystal structures.
Examination of secondary structures, polarity, hydrogen bonding, and hydrophobic interactions.
Comparative analysis of cyclic peptide and small-molecule ligand binding modes.

Main Results:

Protein-bound cyclic peptides exhibit diverse backbone structures, including elements found in protein-protein interfaces.
Cyclic peptides utilize both main chains and side chains for polar contacts and hydrogen bonds with proteins, dispelling the 'privileged scaffold' notion.
Compared to small molecules, cyclic peptides bind larger, polar, and water-exposed protein surfaces, increasing affinity, selectivity, and residence time.

Conclusions:

Cyclic peptides are versatile ligands that engage proteins through extensive polar and hydrogen bond interactions, not solely hydrophobic effects.
Their ability to bind across large, dynamic protein surfaces makes them potent modulators of protein-protein interfaces.
Cyclic peptides offer advantages over small-molecule drugs in terms of affinity, selectivity, and biological activity for certain therapeutic targets.