# Aspartimide Modification in RiPP Natural Products

## TL;DR

This paper explains how a unique chemical modification called aspartimide is formed in certain natural peptides and introduces a new class of these peptides.

## Contribution

The paper reveals that RiPP-associated PIMTs methylate specific Asp residues to form aspartimide and identifies a new RiPP class called imiditides.

## Key findings

- RiPP-associated PIMTs methylate specific Asp residues to form aspartimide, unlike canonical PIMTs.
- Aspartimidylation is a defining feature of a new RiPP class called imiditides or type I pamtides.
- Biochemical details of aspartimide formation are described in lanthipeptides, lasso peptides, and graspetides.

## Abstract

Multiple classes
of ribosomally synthesized and post-translationally
modified peptides (RiPPs) are chemically modified with an enigmatic
functional group, the aspartimide. This modification occurs via the
action of an enzyme related to the protein repair catalyst protein
isoaspartyl methyltransferase (PIMT). Contrary to canonical PIMTs
which methylate isoaspartate residues within a protein, RiPP-associated
PIMTs directly methylate specific Asp residues within the RiPP substrate,
resulting in the formation of an aspartimide. The biochemical details
of aspartimidylation in three RiPP classes, lanthipeptides, lasso
peptides, and graspetides, are described herein. The discovery of
a new class of RiPPs, the imiditides or type I pamtides, with aspartimide
as the class-defining post-translational modification, is also described.
Finally, knowledge gaps as well as suggestions for future research
are discussed.