Finding new posttranslational modifications in salivary proline-rich proteins
Rui Vitorino1, Renato Alves, António Barros
1Department of Chemistry, University of Aveiro, QOPNA, Mass Spectrometry Center, Aveiro, Portugal.
Proteomics
|September 30, 2010
Summary
This study identified 45 new post-translational modifications (PTMs) in salivary proline-rich proteins (PRPs), including glycosylation and phosphorylation. Head and neck cancer patients showed increased N-acetyl hexosamine modification on basic PRPs.
Area of Science:
- Biochemistry
- Proteomics
- Salivary Diagnostics
Background:
- Proline-rich proteins (PRPs) are complex salivary peptides with known post-translational modifications (PTMs).
- Previous studies identified limited serine phosphorylation and glucuronylation sites on acidic (aPRPs) and basic (bPRPs) proline-rich proteins.
Purpose of the Study:
- To identify novel PTMs and distinct isoforms of salivary PRPs.
- To characterize the salivary peptidome across control, diabetic, and head and neck cancer (HNC) patient groups.
Main Methods:
- Liquid chromatography-matrix-assisted laser desorption/ionization-time of flight/time of flight (LC-MALDI-TOF/TOF) mass spectrometry.
- Peptidome characterization of salivary samples from 20 subjects.
Main Results:
- Identification of 45 new PRP-modified residues, primarily glycosylation, phosphorylation, and N-terminal pyro-glutamic acid (pyro-Glu).
- Specific modifications identified include N-glycosylation in bPRP2, bPRP3, and bPRP4; O-glycosylation in bPRP2 and aPRP; and terminal monosaccharide additions.
- Observed allele variants for bPRP1 and bPRP4.
- Predominance of N-acetyl hexosamine modification on bPRPs in HNC patients.
Conclusions:
- Salivary peptidome analysis reveals extensive PRP modifications beyond previously known sites.
- Glycosylation and phosphorylation are major contributors to PRP diversity.
- Altered PRP modification patterns, particularly N-acetyl hexosamine on bPRPs, may serve as potential biomarkers for Head and Neck Cancer.
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