Semi-automated identification of N-Glycopeptides by hydrophilic interaction chromatography, nano-reverse-phase LC-MS/MS, and glycan database search

J Proteome Res. 2012 Mar 2;11(3):1728-40. doi: 10.1021/pr201183w. Epub 2012 Feb 6.

Abstract

Glycoproteins fulfill many indispensable biological functions, and changes in protein glycosylation have been observed in various diseases. Improved analytical methods are needed to allow a complete characterization of this complex and common post-translational modification. In this study, we present a workflow for the analysis of the microheterogeneity of N-glycoproteins that couples hydrophilic interaction and nanoreverse-phase C18 chromatography to tandem QTOF mass spectrometric analysis. A glycan database search program, GlycoPeptideSearch, was developed to match N-glycopeptide MS/MS spectra with the glycopeptides comprised of a glycan drawn from the GlycomeDB glycan structure database and a peptide from a user-specified set of potentially glycosylated peptides. Application of the workflow to human haptoglobin and hemopexin, two microheterogeneous N-glycoproteins, identified a total of 57 distinct site-specific glycoforms in the case of haptoglobin and 14 site-specific glycoforms of hemopexin. Using glycan oxonium ions and peptide-characteristic glycopeptide fragment ions and by collapsing topologically redundant glycans, the search software was able to make unique N-glycopeptide assignments for 51% of assigned spectra, with the remaining assignments primarily representing isobaric topological rearrangements. The optimized workflow, coupled with GlycoPeptideSearch, is expected to make high-throughput semiautomated glycopeptide identification feasible for a wide range of users.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Carbohydrate Sequence
  • Chromatography, Reverse-Phase / methods*
  • Databases, Protein
  • Glycoproteins / chemistry
  • Glycoproteins / isolation & purification*
  • Haptoglobins / chemistry
  • Haptoglobins / isolation & purification
  • Hemopexin / chemistry
  • Hemopexin / isolation & purification
  • Humans
  • Hydrophobic and Hydrophilic Interactions
  • Molecular Sequence Data
  • Peptide Fragments / chemistry
  • Peptide Fragments / isolation & purification
  • Peptide Mapping / methods
  • Polysaccharides / chemistry
  • Polysaccharides / isolation & purification*
  • Protein Isoforms / chemistry
  • Protein Isoforms / isolation & purification
  • Proteolysis
  • Software*
  • Tandem Mass Spectrometry

Substances

  • Glycoproteins
  • Haptoglobins
  • Peptide Fragments
  • Polysaccharides
  • Protein Isoforms
  • Hemopexin