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Phosphorylated serine and threonine residues promote site-specific fragmentation of singly charged, arginine-containing peptide ions


Gehrig, P M; Roschitzki, B; Rutishauser, D; Reiland, S; Schlapbach, R (2009). Phosphorylated serine and threonine residues promote site-specific fragmentation of singly charged, arginine-containing peptide ions. Rapid Communications in Mass Spectrometry, 23(10):1435-1445.

Abstract

In order to investigate gas-phase fragmentation reactions of phosphorylated peptide ions, matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) tandem mass (MS/MS) spectra were recorded from synthetic phosphopeptides and from phosphopeptides isolated from natural sources. MALDI-TOF/TOF (TOF: time-of-flight) spectra of synthetic arginine-containing phosphopeptides revealed a significant increase of y ions resulting from bond cleavages on the C-terminal side of phosphothreonine or phosphoserine. The same effect was found in ESI-MS/MS spectra recorded from the singly charged but not from the doubly charged ions of these phosphopeptides. ESI-MS/MS spectra of doubly charged phosphopeptides containing two arginine residues support the following general fragmentation rule: Increased amide bond cleavage on the C-terminal side of phosphorylated serines or threonines mainly occurs in peptide ions which do not contain mobile protons. In MALDI-TOF/TOF spectra of phosphopeptides displaying N-terminal fragment ions, abundant b-H(3)PO(4) ions resulting from the enhanced dissociation of the pSer/pThr-X bond were detected (X denotes amino acids). Cleavages at phosphoamino acids were found to be particularly predominant in spectra of phosphopeptides containing pSer/pThr-Pro bonds. A quantitative evaluation of a larger set of MALDI-TOF/TOF spectra recorded from phosphopeptides indicated that phosphoserine residues in arginine-containing peptides increase the signal intensities of the respective y ions by almost a factor of 3. A less pronounced cleavage-enhancing effect was observed in some lysine-containing phosphopeptides without arginine. The proposed peptide fragmentation pathways involve a nucleophilic attack by phosphate oxygen on the carbon center of the peptide backbone amide, which eventually leads to cleavage of the amide bond.

In order to investigate gas-phase fragmentation reactions of phosphorylated peptide ions, matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) tandem mass (MS/MS) spectra were recorded from synthetic phosphopeptides and from phosphopeptides isolated from natural sources. MALDI-TOF/TOF (TOF: time-of-flight) spectra of synthetic arginine-containing phosphopeptides revealed a significant increase of y ions resulting from bond cleavages on the C-terminal side of phosphothreonine or phosphoserine. The same effect was found in ESI-MS/MS spectra recorded from the singly charged but not from the doubly charged ions of these phosphopeptides. ESI-MS/MS spectra of doubly charged phosphopeptides containing two arginine residues support the following general fragmentation rule: Increased amide bond cleavage on the C-terminal side of phosphorylated serines or threonines mainly occurs in peptide ions which do not contain mobile protons. In MALDI-TOF/TOF spectra of phosphopeptides displaying N-terminal fragment ions, abundant b-H(3)PO(4) ions resulting from the enhanced dissociation of the pSer/pThr-X bond were detected (X denotes amino acids). Cleavages at phosphoamino acids were found to be particularly predominant in spectra of phosphopeptides containing pSer/pThr-Pro bonds. A quantitative evaluation of a larger set of MALDI-TOF/TOF spectra recorded from phosphopeptides indicated that phosphoserine residues in arginine-containing peptides increase the signal intensities of the respective y ions by almost a factor of 3. A less pronounced cleavage-enhancing effect was observed in some lysine-containing phosphopeptides without arginine. The proposed peptide fragmentation pathways involve a nucleophilic attack by phosphate oxygen on the carbon center of the peptide backbone amide, which eventually leads to cleavage of the amide bond.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Functional Genomics Center Zurich
08 University Research Priority Programs > Systems Biology / Functional Genomics
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Language:English
Date:2009
Deposited On:02 Dec 2009 15:40
Last Modified:05 Apr 2016 13:36
Publisher:Wiley-Blackwell
ISSN:0951-4198
Publisher DOI:https://doi.org/10.1002/rcm.4019
PubMed ID:19353557

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