Conformational consequences of protein glycosylation: Preparation of O-mannosyl serine and threonine building blocks, and their incorporation into glycopeptide sequences derived from α-dystroglycan

Mian Liu, Andrew Borgert, George Barany, David Live

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

With the goal to investigate the structural impact of O-mannosyl glycosylation on α-dystroglycan, a glycoprotein that has an important role in the extracellular organization of muscle, glycopeptides derived from its mucin-like sequence have been prepared by solid-phase peptide synthesis. Two approaches have been explored to obtain needed mannosylated serine and threonine building blocks. With the α-carboxyl group unprotected, and with tetraaceto-1-fluoro-α-D-mannose as the sugar donor, the desired α-O-mannosyl-Fmoc-Ser/Thr formed, along with mannosyl ester isomers and the species with mannose attached to both hydroxyl and carboxyl functions. Relevant mechanistic questions and stability issues were elucidated. Alternatively, building blocks were made with the α-carboxyl protected/activated as the pentafluorophenyl (Pfp) ester. Glycopeptides synthesized herein contained 5-9 residues, and featured one, two, and four consecutive Ser and/or Thr residues o-glycosylated with mannose. Circular dichroism (CD) spectra for Man-containing glycopeptides recorded in water show them to be not well ordered. For one of the α-dystroglycan-derived sequences, the comparative conformational consequences of glycosylation by either Man or GalNAc have been examined by CD and NMR, with both methods showing a more organized structure when GalNAc is present.

Original languageEnglish (US)
Pages (from-to)358-368
Number of pages11
JournalBiopolymers - Peptide Science Section
Volume90
Issue number3
DOIs
StatePublished - 2008

Keywords

  • Alpha dystroglycan
  • Mannose glycopeptides
  • Mannosylated building blocks
  • NMR
  • Solid-phase synthesis

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