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ACS Chem Biol. 2017 Apr 21;12(4):922-927. doi: 10.1021/acschembio.6b01069. Epub 2017 Mar 3.

Lysine-Tryptophan-Crosslinked Peptides Produced by Radical SAM Enzymes in Pathogenic Streptococci.

Author information

1
Departments of Chemistry and ‡Molecular Biology, Princeton University , Princeton, New Jersey 08544, United States.

Abstract

Macrocycles represent a common structural framework in many naturally occurring peptides. Several strategies exist for macrocyclization, and the enzymes that incorporate them are of great interest, as they enhance our repertoire for creating complex molecules. We recently discovered a new peptide cyclization reaction involving a crosslink between the side chains of lysine and tryptophan that is installed by a radical SAM enzyme. Herein, we characterize relatives of this metalloenzyme from the pathogens Streptococcus agalactiae and Streptococcus suis. Our results show that the corresponding enzymes, which we call AgaB and SuiB, contain multiple [4Fe-4S] clusters and catalyze Lys-Trp crosslink formation in their respective substrates. Subsequent high-resolution-MS and 2D-NMR analyses located the site of macrocyclization. Moreover, we report that AgaB can accept modified substrates containing natural or unnatural amino acids. Aside from providing insights into the mechanism of this unusual modification, the substrate promiscuity of AgaB may be exploited to create diverse macrocyclic peptides.

PMID:
28191919
DOI:
10.1021/acschembio.6b01069
[Indexed for MEDLINE]

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