Cellulonodin-2 and Lihuanodin: Lasso Peptides with an Aspartimide Post-Translational Modification.

TitleCellulonodin-2 and Lihuanodin: Lasso Peptides with an Aspartimide Post-Translational Modification.
Publication TypeJournal Article
Year of Publication2021
AuthorsCao, L, Beiser, M, Koos, JD, Orlova, M, Elashal, HE, Schröder, HV, A Link, J
JournalJ Am Chem Soc
Date Published2021 08 04
KeywordsAspartic Acid, Bacillales, Peptides, Protein D-Aspartate-L-Isoaspartate Methyltransferase, Protein Processing, Post-Translational, Thermobifida

<p>Lasso peptides are a family of ribosomally synthesized and post-translationally modified peptides (RiPPs) defined by their threaded structure. Besides the class-defining isopeptide bond, other post-translational modifications (PTMs) that further tailor lasso peptides have been previously reported. Using genome mining tools, we identified a subset of lasso peptide biosynthetic gene clusters (BGCs) that are colocalized with genes encoding protein l-isoaspartyl methyltransferase (PIMT) homologues. PIMTs have an important role in protein repair, restoring isoaspartate residues formed from asparagine deamidation to aspartate. Here we report a new function for PIMT enzymes in the post-translational modification of lasso peptides. The PIMTs associated with lasso peptide BGCs first methylate an l-aspartate side chain found within the ring of the lasso peptide. The methyl ester is then converted into a stable aspartimide moiety, endowing the lasso peptide ring with rigidity relative to its unmodified counterpart. We describe the heterologous expression and structural characterization of two examples of aspartimide-modified lasso peptides from thermophilic Gram-positive bacteria. The lasso peptide cellulonodin-2 is encoded in the genome of actinobacterium , while lihuanodin is encoded in the genome of firmicute . Additional genome mining revealed PIMT-containing lasso peptide BGCs in 48 organisms. In addition to heterologous expression, we have reconstituted PIMT-mediated aspartimide formation in vitro, showing that lasso peptide-associated PIMTs transfer methyl groups very rapidly as compared to canonical PIMTs. Furthermore, in stark contrast to other characterized lasso peptide PTMs, the methyltransferase functions only on lassoed substrates.</p>

Alternate JournalJ Am Chem Soc
PubMed ID34283601
PubMed Central IDPMC9206484
Grant ListR01 GM107036 / GM / NIGMS NIH HHS / United States