@article{nokey,

title = {Leader-Independent C-Terminal Modification by a Radical S-Adenosyl-l-methionine Maturase Enables Macrocyclic GLP-1-Like Peptides},

author = {Pedigo, Jacob K. and Eastman, Karsten A. S. and Bandarian, Vahe},

url = {https://doi.org/10.1021/acsbiomedchemau.5c00152},

doi = {10.1021/acsbiomedchemau.5c00152},

year  = {2025},

date = {2025-10-14},

journal = {ACS Bio & Med Chem Au},

abstract = {Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a rapidly expanding family of natural products in which biosynthetic maturase enzymes tailor ribosomal precursors into bioactive products. Classical RiPP maturation relies on an N-terminal leader sequence in the precursor peptide and a complementary RiPP-recognition element in the enzyme to guide substrate binding. Herein, we interrogated PapB, a radical S-adenosyl-l-methionine RiPP maturase known to introduce thio(seleno)-ether cross-links and discovered that its catalytic reach extends well beyond this paradigm. PapB efficiently processes substrates that lack any canonical leader sequence, demonstrating bona fide leader-independent activity. To highlight the practical value of this capability, we applied PapB to three therapeutically relevant analogues of glucagon-like peptide pathway agonists to generate C-terminal cyclic structures. In every case, the enzyme achieved complete conversion of the linear to the thioether macrocyclized peptide. These results establish PapB as a versatile, plug-and-play biocatalyst for late-stage macrocyclization of structurally diverse peptides, opening a direct route to conformationally constrained therapeutic candidates without the need for leader tags.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@article{Eastman2023,

title = {A Promiscuous rSAM Enzyme Enables Diverse Peptide Cross-linking},

author = {Karsten A. S. Eastman and Marcus C. Mifflin and Paul F. Oblad and Andrew G. Roberts and Vahe Bandarian},

doi = {10.1021/acsbiomedchemau.3c00043},

issn = {2694-2437},

year  = {2023},

date = {2023-12-20},

urldate = {2023-12-20},

journal = {ACS Bio Med Chem Au},

volume = {3},

number = {6},

pages = {480--493},

keywords = {Biochemistry, Drug Discovery, Molecular Biology, Pharmaceutical Science},

pubstate = {published},

tppubtype = {article}

}

@article{Eastman2023c,

title = {Intermolecular electron transfer in radical SAM enzymes as a new paradigm for reductive activation},

author = {Karsten A. S. Eastman and Andrew S. Jochimsen and Vahe Bandarian},

doi = {10.1016/j.jbc.2023.105058},

issn = {0021-9258},

year  = {2023},

date = {2023-09-00},

journal = {Journal of Biological Chemistry},

volume = {299},

number = {9},

keywords = {Biochemistry, Cell Biology, Molecular Biology},

pubstate = {published},

tppubtype = {article}

}

@article{Rush2023,

title = {Peptide Selenocysteine Substitutions Reveal Direct Substrate–Enzyme Interactions at Auxiliary Clusters in Radical \textit{S}-Adenosyl-<scp>l</scp>-methionine Maturases},

author = {Katherine W. Rush and Karsten A. S. Eastman and William M. Kincannon and Ninian J. Blackburn and Vahe Bandarian},

doi = {10.1021/jacs.3c00831},

issn = {1520-5126},

year  = {2023},

date = {2023-05-10},

journal = {J. Am. Chem. Soc.},

volume = {145},

number = {18},

pages = {10167-10177},

keywords = {Biochemistry, Catalysis, Colloid and Surface Chemistry, General Chemistry},

pubstate = {published},

tppubtype = {article}

}

@article{Eastman2022,

title = {Leveraging Substrate Promiscuity of a Radical \textit{S}-Adenosyl-<scp>L</scp>-methionine RiPP Maturase toward Intramolecular Peptide Cross-Linking Applications},

author = {Karsten A. S. Eastman and William M. Kincannon and Vahe Bandarian},

doi = {10.1021/acscentsci.2c00501},

issn = {2374-7951},

year  = {2022},

date = {2022-08-24},

journal = {ACS Cent. Sci.},

volume = {8},

number = {8},

pages = {1209-1217},

keywords = {General Chemical Engineering, General Chemistry},

pubstate = {published},

tppubtype = {article}

}