Dataset Information

Confident identification of citrullinated peptides from P gingivalis

ABSTRACT: Porphyromonas gingivalis is a key pathogen in the development of chronic periodontitis and has recently been linked to the development of rheumatoid arthritis and Alzheimer’s disease. In this project the outer membrane vesicles (OMV) from Pg have been analyzed using a two-dimensional HFBA-based separation system combined with LC-MS. Three strains from P. gingivalis was analyzed in order to elucidate their citrullinome: wild-type (WT), a mutant with the active site cysteine mutated to alanine (C351A), as well as a knock-out mutant of peptidyl arginine deiminase (ΔPPAD). For optimal and positive identification and validation of citrullinated peptides and proteins, high resolution mass spectrometers and strict MS criteria were utilized. This may have compromised the total number of identified citrullination, but increased the confidence of the validation. A new 2D separation system proved to increase the strength of validation, and along with the use of an in-house build program, Citrullia, we establish a fast and easy semi-automatic (manual) validation of citrullinated peptides. For WT we identified 78 citrullinated proteins having a total of 161 citrullination sites. For C351A a single citrullination site was found and no citrullinations was found for ΔPPAD.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Porphyromonas Gingivalis (strain Atcc Baa-308 / W83)

SUBMITTER: Peter Højrup

LAB HEAD: Peter Højrup

PROVIDER: PXD015701 | Pride | 2019-11-22

REPOSITORIES: Pride

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Publications

Citrullinome of Porphyromonas gingivalis Outer Membrane Vesicles: Confident Identification of Citrullinated Peptides.

Larsen Daniel Nyberg DN Mikkelsen Christian Engelbrecht CE Kierkegaard Mads M Bereta Grzegorz P GP Nowakowska Zuzanna Z Kaczmarek Jakub Z JZ Potempa Jan J Højrup Peter P

Molecular & cellular proteomics : MCP 20191121 1

Porphyromonas gingivalis is a key pathogen in chronic periodontitis and has recently been mechanistically linked to the development of rheumatoid arthritis via the activity of peptidyl arginine deiminase generating citrullinated epitopes in the periodontium. In this project the outer membrane vesicles (OMV) from P. gingivalis W83 wild-type (WT), a W83 knock-out mutant of peptidyl arginine deiminase (ΔPPAD), and a mutant strain expressing PPAD with the active site cysteine mutated t ...[more]

PMID: 31754044

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Project description:Citrullination is a post-translational modification of arginine catalyzed by five peptidylarginine deiminases (PADs) in humans. The loss of a positive charge may cause structural or functional alterations and while the modification has been linked to several diseases including rheumatoid arthritis and cancer, its physiological or pathophysiological roles remain largely unclear. In part this is owing to limitations in available methodology able to robustly enrich, detect and localize the modification. As a result, only few citrullination sites have been identified on human proteins with high confidence. In this study, we mined data from mass spectrometry-based deep proteomic profiling of 30 human tissues to identify citrullination sites on endogenous proteins. Database searching of ~70 million tandem mass spectra yielded ~13,000 candidate spectra which were further triaged by spectrum quality metrics and the detection of the specific neutral loss of isocyanic acid from citrullinated peptides to reduce false positives. Because citrullination is easily confused with deamidation, we synthetised ~2,200 citrullinated and 1,300 deamindated peptides to build a library of reference spectra. This led to the validation of 375 citrullination sites on 209 human proteins. Further analysis showed that >80% of the identified modifications sites were new and for 56% of the proteins, citrullination was detected for the first time. Sequence motif analysis revealed a strong preference for Asp and Gly, residues around the citrullination site. Interestingly, while the modification was detected in 26 human tissues with the highest levels found in brain and lung, citrullination levels did not correlate well with protein expression of the PAD enzymes. Even though the current work represents the largest survey of protein citrullination to date, the modification was mostly detected on high abundance proteins arguing that the development of specific enrichment methods would be required in order to study the full extent of cellular protein citrullination.

Dataset Information

Confident identification of citrullinated peptides from P gingivalis

Publications

Citrullinome of <i>Porphyromonas gingivalis</i> Outer Membrane Vesicles: Confident Identification of Citrullinated Peptides.

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