Postligation-Desulfurization: A General Approach for Chemical Protein Synthesis

Abstract

Native chemical ligation, involving regioselective and chemoselective coupling of two unprotected peptide segments, enabled the synthesis of polypeptide with more than 200 amino acids. However, cysteine was indispensable in this synthetic technique in its initial format, which limited its further application. Thus, considerable effort has been put into breaking the restriction of cysteine-containing ligation. As a consequence, postligation-desulfurization, concerning thiol-mediated ligation followed by desulfurization, was developed. This review describes the development and recent progress on the chemical synthesis of peptides and proteins encompassing postligation-desulfurization at alanine, valine, lysine, threonine, leucine, proline, arginine, aspartic acid, glutamate, phenylalanine, glutamine, and tryptophan.

Visible-Light-Mediated Modification and Manipulation of Biomacromolecules

“…8 Therefore, postligation desulfurization of cysteine residues is a useful tool for the synthesis of cysteine-free peptides via NCL. 65 An efficient visible-light-photocatalyzed desulfurization of cysteine to alanine was developed by Guo and co-workers (Scheme 6). 66 Using the photocatalyst [Ru(bpy) 3 ] 2+ and an excess of the water-soluble phosphine 3,3′,3″-phosphanetriyltris-(benzenesulfonic acid) trisodium salt (TPPTS, 18), desulfurization of complex peptides was achieved in water or aqueous phosphate buffer.…”

“…This transformation is particularly valuable in the context of native chemical ligation (NCL), a cysteine-dependent approach to synthesize a contiguous polypeptide from two smaller fragments. − Since NCL invariably results in a ligation site marked by cysteine, retrosynthetic design of peptide fragments is usually restricted to disconnection at this residue, a limitation only compounded by the low natural abundance of cysteine in proteins . Therefore, postligation desulfurization of cysteine residues is a useful tool for the synthesis of cysteine-free peptides via NCL …”

Using Chemical Synthesis To Study and Apply Protein Glycosylation

“…However, in reality, many difficulties were found before they could realize this concept. The main reason was that desulfurization conditions known at the time were not compatible with Cys protecting groups and/or led to product degradation in many cases. , Through extensive investigation, the Danishefsky group was able to identify reaction conditions that were compatible with the synthesis of many long glycopeptides and glycoproteins . This was clearly demonstrated in the synthesis of glycosylated EPO (Figure ).…”

Visible‐light photoredox‐catalyzed desulfurization of thiol‐ and disulfide‐containing amino acids and small peptides

“…Likewise, desulfurizations are of great importance to remove sulfur from compounds that would otherwise be harmful for the environment or act as poison in catalytic transformations. Moreover, since the introduction in the nineties of the cysteine‐mediated native chemical ligation (NCL) approach for the (semi)synthesis of proteins, the desulfurization reaction has also become very useful for peptide and protein chemists . Indeed, desulfurization of cysteine converts this residue into alanine: therefore, besides natural cysteine residues, also, natural alanine residues along the sequence can be selected as ligation sites, which are temporarily replaced by cysteine to perform the ligation and then converted to alanine by desulfurization .…”