Unlocking the Silent Proteome: Chemoselective Asn/Gln Activation for Multidimensional Protein Diversification

Area of Science:

• Biochemistry and Chemical Biology
• Organic Synthesis and Medicinal Chemistry

Background:

• Amide groups in asparagine (Asn) and glutamine (Gln) are abundant in biomolecules but difficult to modify selectively.
• The low reactivity and chelating properties of these residues hinder their chemical manipulation in peptides and proteins.

Purpose of the Study:

• To develop a general and chemoselective strategy for modifying Asn and Gln residues in native peptides and proteins.
• To create bioorthogonal nitrile handles from primary amides for further diversification.

Main Methods:

• Conversion of primary amides in Asn and Gln to bioorthogonal nitrile handles.
• Carbometalation of nitriles with aryl boronic acids to synthesize aryl ketones.
• Application of the method to native peptides, proteins, and antibody modification.

Main Results:

• Demonstrated a general strategy for selective conversion of Asn/Gln amides into nitrile handles.
• Achieved chemoselective modification of native peptides and proteins, including antibody-fluorophore conjugation.
• Enabled synthesis of unnatural amino acids, peptide diversification, and fluorosequencing of Asn residues.

Conclusions:

• The developed method provides a versatile and selective route for modifying Asn and Gln residues.
• Expands the accessible chemical space of biomolecules and facilitates the study of the 'chemically silent' proteome.
• Offers a powerful tool for site-selective protein modification and the synthesis of complex bioconjugates.