Sulfated Glycoprotein Synthesis

Abstract

Chemical protein synthesis has achieved tremendous progress in the past decades. With the development of chemical ligation as powerful tools, the scope of synthetic protein is greatly expanded. Proteoglycans are a class of sulfated glycoproteins widely distributed on the cell surface and in the extracellular matrix, which are extensively engaged in cellular communication events. Consisting of protein backbone and glycosaminoglycan(s) side chain, proteoglycans are highly complex and heterogeneous in nature. Chemical synthesis provides facile and reliable approach to these molecules, with defined glycan structure and sulfation pattern. One remaining problem is that the acid-labile sulfates could hardly survive during the typical solid phase peptide synthesis (SPPS) process. In this chapter, strategic design of a "glycopeptide cassette" for the preparation of sulfated glycoprotein is described. In particular, we provide protocols for the chemical synthesis of ectodomain fragment (23-120) of sulfated glycoprotein syndecan-1.

Keywords: Glycopeptide cassette; Heparan sulfates; Protein chemical ligation; Proteoglycan; Sulfated glycoprotein.

Fig. 1

Preparation of glycoproteins

Fig. 2

General overview of the synthetic scheme toward syndecan-1 ectodomain (23–120) 1

Fig. 3

Characterization of synthetic sulfated glycopeptide fragment 6 and syndecan-1 ectodomain (23–120) 1. (a) and (b) HPLC and ESI-MS characterization of sulfated glycopeptide fragment 6. (c) and (d) HPLC and ESI-MS characterization of syndecan-1 ectodomain (23–120) 1. (e) and F) NMR (¹H and TOCSY) characterization of syndecan-1 ectodomain (23–120) 1. Signals from each proton of the xyloside can be clearly assigned

Fig. 4

Use solid phase peptide synthesis to assemble the peptide fragments 5, 11, and 12

Fig. 5

Preparation of the sulfated “glycopeptide cassette”