Solid-phase synthesis and evaluation of glycopeptide fragments from rat epididymal cysteine-rich secretory protein-1 (Crisp-1)

Mian Liu, David W. Hamilton, George Barany

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Three 18-residue peptides with the sequence Glp-Asp-Thr-Thr-Asp-Glu-Trp- Asp-Arg-Asp-Leu-Glu-Asn-Leu-Ser-Thr-Thr-Lys, taken from the N-terminus of the rat epididymal cysteine-rich secretory protein (Crisp-1) that is important in the fertilization process, were prepared by Fmoc solid-phase synthesis using a convergent strategy. These peptides were the parent sequence, plus two possible α-O-linked TN antigen-containing glycopeptides with a Thr(α-D-GalNAc) residue in place of either Thr3 or Thr 4. During chain assembly, two deletion peptides [des-Asp2 and des-Thr(Ac3-α-D-GalNAc)] and one terminated peptide [N-acetylated 14-mer] arose, as did several peptides in which aspartimide formation had occurred at each of the four possible positions in the sequence. These by-products totaled ∼20% of the desired product; they were recognized by HPLC and ESI-MS and removed during the intermediate purifications. Final products, obtained in 15-21% overall yields, were characterized by HPLC purities and ESI-MS. Circular dichroism (CD) spectra for all three purified peptides, recorded in pure water and in trifluoroethanol-H2O (1:1), revealed that the presence of a sugar moiety does not significantly impact the sampled conformations. Future biological evaluation could elucidate the nature and locus of sugar modification of Crisp-1, and provide insight as to why Crisp-1 protein E binds sperm irreversibly, in contrast to protein D that lacks a sugar near the N-terminus and only binds sperm loosely.

Original languageEnglish (US)
Pages (from-to)6399-6410
Number of pages12
JournalMolecules
Volume15
Issue number9
DOIs
StatePublished - Sep 2010

Keywords

  • Circular dichroism
  • Cysteine-rich secretory protein (Crisp-1)
  • Glycopeptides
  • Solid-phase synthesis
  • T antigen

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