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Phage display, an ingenious invention for evaluating peptide libraries, has been limited to natural peptides that are ribosomally assembled with proteinogenic amino acids. Recently, there has been growing interest in chemically modifying phage libraries to create nonnatural cyclic and multicyclic peptides, which are appealing for use as inhibitors of protein–protein interactions. While earlier reports largely focused on side-chain side-chain cyclization, we report herein a novel strategy for creating backbone-side chain cyclized peptide libraries on phage. Our strategy capitalizes on the unique reactivity of an N-terminal cysteine (NCys) with 2-cyanobenzothiazole (CBT) which, in conjugation with another thiol-reactive group, can elicit rapid cyclization between an NCys and an internal cysteine. The resulting library was screened against two model proteins, namely Keap1 and Sortase A. The screening readily revealed potent inhibitors for both proteins with certain Keap1 ligands reaching low nanomolar potency. The backbone-side chain cyclization strategy described herein presents a significant addition to the toolkit of creating nonnatural macrocyclic peptide libraries for phage display.
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A Cysteine‐Directed Proximity‐Driven Crosslinking Method for Native Peptide Bicyclization
Abstract Efficient and site‐specific modification of native peptides and proteins is desirable for synthesizing antibody‐drug conjugates as well as for constructing chemically modified peptide libraries using genetically encoded platforms such as phage display. In particular, there is much interest in efficient multicyclization of native peptides due to the appeals of multicyclic peptides as therapeutics. However, conventional approaches for multicyclic peptide synthesis require orthogonal protecting groups or non‐proteinogenic clickable handles. Herein, we report a cysteine‐directed proximity‐driven strategy for the constructing bicyclic peptides from simple natural peptide precursors. This linear to bicycle transformation initiates with rapid cysteine labeling, which then triggers proximity‐driven amine‐selective cyclization. This bicyclization proceeds rapidly under physiologic conditions, yielding bicyclic peptides with a Cys‐Lys‐Cys, Lys‐Cys‐Lys or N‐terminus‐Cys‐Cys stapling pattern. We demonstrate the utility and power of this strategy by constructing bicyclic peptides fused to proteins as well as to the M13 phage, paving the way to phage display of novel bicyclic peptide libraries.
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- Award ID(s):
- 2204078
- PAR ID:
- 10425398
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 62
- Issue:
- 31
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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