PhosphoShield : Improving Trypsin Digestion of Phosphoproteins by Shielding the Negatively Charged Phosphate Moiety

Protein phosphorylation is a post-translational modification that is essential to cellular signaling, cellular function, and associated disease progression. Bottom-up proteomics based on enzymatic digestion is the most widely used approach for identifying and quantifying phosphoproteins in complex biological samples. Researchers have largely optimized the experimental conditions for trypsin digestion, and it is now a routine procedure. However, trypsin digestion is impaired by the presence of phosphorylated residues in the protein sequence. This impairment arises from the fact that there are commonly salt bridges between a negatively charged phosphate group and the side chain of protonated arginine or lysine. On average, 55% of all phosphopeptides have their phosphosites located less than three amino acid residues from a cleavage site. Salt bridges reduce the cleavage accessibility for trypsin by masking the basic site chain groups of arginine and lysine. Thus, there are frequent missed cleavages in the vicinity of phosphorylation sites, thereby lessening both the depth of proteome coverage and the quantification accuracy of phosphoproteomics. In this work, we propose a method termed PhosphoShield to mitigate salt bridge formation by adding a digallium complex that exhibits a high binding affinity to the phosphate group. We tested our method using quantitative mass spectrometry analysis of the phosphoproteome of human liver cancer cells (HepG2). PhosphoShield enhances the cleavage frequency of at least 17% of tryptic phosphopeptides having cleavage sites close to the phosphate group.

Medienart:

E-Artikel

Erscheinungsjahr:

2020

Erschienen:

2020

Enthalten in:

Zur Gesamtaufnahme - volume:31

Enthalten in:

Journal of the American Society for Mass Spectrometry - 31(2020), 10 vom: 07. Okt., Seite 2053-2060

Sprache:

Englisch

Beteiligte Personen:

Bubis, Julia A [VerfasserIn]
Gorshkov, Vladimir [VerfasserIn]
Gorshkov, Mikhail V [VerfasserIn]
Kjeldsen, Frank [VerfasserIn]

Links:

Volltext

Themen:

Digallium complex
EC 3.4.21.4
Journal Article
Metal affinity
Missed cleavages
Phosphates
Phosphopeptides
Phosphoproteins
Phosphoproteomics
Sample preparation
Trypsin
Trypsin digestion

Anmerkungen:

Date Completed 13.07.2021

Date Revised 13.07.2021

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1021/jasms.0c00171

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM314137815