Publications
2025
Eastman, Karsten A. S.; Roberts, Andrew G.; Bandarian, Vahe
Diverse thioether macrocyclized peptides through a radical SAM maturase Journal Article
In: PNAS, vol. 122, no. 34, 2025.
Abstract | Links | BibTeX | Tags: Biochemistry, Enzymes, Mechanism, Peptides, Unnatural Amino Acids
@article{Eastman2025,
title = {Diverse thioether macrocyclized peptides through a radical SAM maturase},
author = {Karsten A. S. Eastman and Andrew G. Roberts and Vahe Bandarian },
editor = {Amy Rosenzweig},
doi = {10.1073/pnas.2512563122},
year = {2025},
date = {2025-08-21},
urldate = {2025-08-21},
journal = {PNAS},
volume = {122},
number = {34},
abstract = {Disulfide bonds stabilize many bioactive peptides, but their susceptibility to reduction under physiological conditions limits broad applicability in biotechnology. PapB is a promiscuous radical S-adenosyl-L-methionine enzyme that is involved in the maturation of PapA, which is a ribosomally produced and posttranslationally modified polypeptide. PapB introduces six thioether linkages between internal Cys residues and carbon atom that is α to the side-chain carboxylate of Asp/Glu residues C-terminal to the Cys residues. Herein, we show that PapB also efficiently couples an internal Cys thiol to the C-terminal carboxylate of peptides terminating in D- or β-amino acids, forming α- or β-thioether macrocycles. Moreover, PapB tolerates β- and N-methyl amino acids within the peptide, resulting in the formation of macrocycles that are comprised entirely of unnatural amino acids, such as peptides containing all β-residues. These findings establish PapB as a sequence-agnostic thioether ligase for efficient C-terminal macrocyclization. Our work expands the enzymatic toolbox for constructing conformationally constrained peptides for therapeutics and chemical biology.},
keywords = {Biochemistry, Enzymes, Mechanism, Peptides, Unnatural Amino Acids},
pubstate = {published},
tppubtype = {article}
}
Disulfide bonds stabilize many bioactive peptides, but their susceptibility to reduction under physiological conditions limits broad applicability in biotechnology. PapB is a promiscuous radical S-adenosyl-L-methionine enzyme that is involved in the maturation of PapA, which is a ribosomally produced and posttranslationally modified polypeptide. PapB introduces six thioether linkages between internal Cys residues and carbon atom that is α to the side-chain carboxylate of Asp/Glu residues C-terminal to the Cys residues. Herein, we show that PapB also efficiently couples an internal Cys thiol to the C-terminal carboxylate of peptides terminating in D- or β-amino acids, forming α- or β-thioether macrocycles. Moreover, PapB tolerates β- and N-methyl amino acids within the peptide, resulting in the formation of macrocycles that are comprised entirely of unnatural amino acids, such as peptides containing all β-residues. These findings establish PapB as a sequence-agnostic thioether ligase for efficient C-terminal macrocyclization. Our work expands the enzymatic toolbox for constructing conformationally constrained peptides for therapeutics and chemical biology.