Site‐Selective Modification of Peptides and Proteins via Interception of Free‐Radical‐Mediated Dechalcogenation

Rhys C Griffiths,Jed E Long,Nicholas J Mitchell,Huw E L Williams,Robert Layfield,Frances R Smith

doi:10.1002/ange.202006260

Abstract

AbstractThe development of site‐selective chemistry targeting the canonical amino acids enables the controlled installation of desired functionalities into native peptides and proteins. Such techniques facilitate the development of polypeptide conjugates to advance therapeutics, diagnostics, and fundamental science. We report a versatile and selective method to functionalize peptides and proteins through free‐radical‐mediated dechalcogenation. By exploiting phosphine‐induced homolysis of the C−Se and C−S bonds of selenocysteine and cysteine, respectively, we demonstrate the site‐selective installation of groups appended to a persistent radical trap. The reaction is rapid, operationally simple, and chemoselective. The resulting aminooxy linker is stable under a variety of conditions and selectively cleavable in the presence of a low‐oxidation‐state transition metal. We have explored the full scope of this reaction using complex peptide systems and a recombinantly expressed protein.

Highlights

The diverse array of chemical functionality displayed by the 20 canonical amino acids presents both a challenge and an opportunity for the site-selective functionalization of peptides and proteins
The reaction was observed to proceed at a slightly etry of TEMPO, which will carry the desired group for slower rate if the excess of TCEP was dropped to 25 equiv. conjugation, led us to conclude that entry 10 represented the and failed to reach completion over 16 hrs with 5 equiv. optimal set of conditions to take forward (referred to (Figure 4 B)
We have developed a novel approach to siteselective polypeptide modification via trapping of freeradical-mediated dechalcogenation

Summary

Introduction

The diverse array of chemical functionality displayed by the 20 canonical amino acids presents both a challenge and an opportunity for the site-selective functionalization of peptides and proteins. The reactions were diluted with buffer and DMSO (up to 20 % co-solvent) to give the final concentrations as described by conjugation protocol A: 2.5 mM peptide wrt selenol monomer, 125 mM TCEP (50 equiv.), 5 mM TEMPO (2 equiv.), 10 mM Mn(OAc)3 (4 equiv.).

Results

Conclusion