N‑Terminal Modification of Proteins with o‑Aminophenols

• Published in: Journal of the American Chemical Society Vol. 136; no. 27; pp. 9572 - 9579
• Main Authors: Obermeyer, Allie C, Jarman, John B, Francis, Matthew B
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 09.07.2014
• Subjects: Aminophenols - chemistry; Models, Molecular; Molecular Structure; Oxidation-Reduction; Peptides - chemistry; Proline - chemistry; Proteins - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja500728c

The synthetic modification of proteins plays an important role in chemical biology and biomaterials science. These fields provide a constant need for chemical tools that can introduce new functionality in specific locations on protein surfaces. In this work, an oxidative strategy is demonstrated for the efficient modification of N-terminal residues on peptides and N-terminal proline residues on proteins. The strategy uses o-aminophenols or o-catechols that are oxidized to active coupling species in situ using potassium ferricyanide. Peptide screening results have revealed that many N-terminal amino acids can participate in this reaction, and that proline residues are particularly reactive. When applied to protein substrates, the reaction shows a stronger requirement for the proline group. Key advantages of the reaction include its fast second-order kinetics and ability to achieve site-selective modification in a single step using low concentrations of reagent. Although free cysteines are also modified by the coupling reaction, they can be protected through disulfide formation and then liberated after N-terminal coupling is complete. This allows access to doubly functionalized bioconjugates that can be difficult to access using other methods.