Total Synthesis of Glycosylated Proteins

Abstract

Glycoproteins are an important class of naturally occurring biomolecules which play a pivotal role in many biological processes. They are biosynthesized as complex mixtures of glycoforms through post-translational protein glycosylation. This fact, together with the challenges associated with producing them in homogeneous form, has hampered detailed structure-function studies of glycoproteins as well as their full exploitation as potential therapeutic agents. By contrast, chemical synthesis offers the unique opportunity to gain access to homogeneous glycoprotein samples for rigorous biological evaluation. Herein, we review recent methods for the assembly of complex glycopeptides and glycoproteins and present several examples from our laboratory towards the total chemical synthesis of clinically relevant glycosylated proteins that have enabled synthetic access to full-length homogeneous glycoproteins.

Exploring chemoselective S-to-N acyl transfer reactions in synthesis and chemical biology

“…X-ray crystallography structures of the semisynthetic protein demonstrated that the ability of the channel to adapt its structure differently for K + and Na + ions is a fundamental aspect of ion selectivity 95 . A detailed discussion of these synthetic endeavours is beyond the scope of this review but readers are referred to a number of excellent recent reviews 11 96 97 98 99 . Of particular interest for applications in chemical and molecular biology are proteins displaying defined PTMs such as glycosylation that can be prepared using this approach.…”

Molecular-scale features that govern the effects of O-glycosylation on a carbohydrate-binding module

“… 4 – 7 Unfortunately, unlike N -glycosylation, no universal consensus sequence has been identified for O -glycosylation, which seriously limits access to glyco-variants and hampers the detailed study and application of O -glycosylation. 8 – 11 …”

“…Since chemical glycosylation is not controlled by the structural features of peptides, it is capable of generating almost any glyco-variant. 8 , 9 , 11 Synthesis of CBM isoforms was conducted with Fmoc-based solid-phase peptide synthesis (SPPS). During SPPS, all sugar hydroxyl and/or phosphate groups on the side chains of the glycoamino acid building blocks where protected as acetyl 16 or benzyl esters, 21 respectively, which are stable during peptide coupling procedures and easily removed under carbohydrate-compatible conditions.…”

Synthesis of l‐ and d‐Ubiquitin by One‐Pot Ligation and Metal‐Free Desulfurization

“…Racemic X‐ray crystallography was employed to characterize the synthetic ubiquitin. We hope that the utility of this one‐pot NCL‐MFD approach can be demonstrated in the chemical synthesis of post‐translational modified proteins (e.g., glycosylated proteins, lipidated proteins, ubiquitinated proteins, and histone derivatives) in future studies.…”