Enhanced methylarginine characterization by post-translational modification-specific targeted data acquisition and electron-transfer dissociation mass spectrometry.
When localizing protein post-translational modifications (PTMs) using liquid-chromatography (LC)-tandem mass spectrometry (MS/MS), existing implementations are limited by inefficient selection of PTM-carrying peptides for MS/MS, particularly when PTM site occupancy is sub-stoichiometric. The present contribution describes a method by which peptides carrying specific PTMs of interest-in this study, methylarginines-may be selectively targeted for MS/MS: peptide features are extracted from high mass accuracy single-stage MS data, searched against theoretical PTM-carrying peptide masses, and matching features are subjected to targeted data acquisition LC-MS/MS. Using trypsin digested Saccharomyces cerevisiae Npl3, in which evidence is presented for 18 methylarginine sites-17 of which fall within a glycine-arginine-rich (GAR) domain spanning <120 amino acids-it is shown that this approach outperforms conventional data dependent acquisition (DDA): when applied to a complex protein mixture featuring in vivo methylated Npl3, 95% more (P=0.030) methylarginine-carrying peptides are selected for MS/MS than DDA, leading to an 86% increase (P=0.044) in the number of methylated peptides producing Mascot ion scores ≥20 following electron-transfer dissociation (ETD). Notably, significantly more low abundance arginine methylated peptides (maximum ion intensities <6×10(4) cps) are selected for MS/MS using this approach relative to DDA (50% more in a digest of purified in vitro methylated Npl3). It is also demonstrated that relative to collision-induced dissociation (CID), ETD facilitates a 586% increase (P=0.016) in average Mascot ion scores of methylarginine-carrying peptides. The present PTM-specific targeted data acquisition approach, though described using methylarginine, is applicable to any ionizable PTM of known mass.
NSW Systems Biology Initiative, University of New South Wales, Sydney, New South Wales, Australia.
Gene
G
Hart-Smith
Jason K K
JK
Low
Melissa A
MA
Erce
Marc R
MR
Wilkins
D001120:Arginine / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D008745:Methylation; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry*; D010449:Peptide Mapping / Q000379:methods; D011499:Protein Processing, Post-Translational; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D053719:Tandem Mass Spectrometry / Q000379:methods*
C077734:NPL3 protein, S cerevisiae; D009687:Nuclear Proteins; D010446:Peptide Fragments; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D001120:Arginine