Ultra acidic strong cation exchange enabling the efficient enrichment of basic phosphopeptides

Area of Science:

• Proteomics
• Biochemistry
• Analytical Chemistry

Background:

• Phosphopeptide enrichment is crucial for studying protein phosphorylation.
• Current methods often under-represent phosphopeptides with multiple basic residues.
• Identifying targets of basophilic kinases is important for understanding cellular signaling.

Purpose of the Study:

• To develop a straightforward method for enriching phosphopeptides with multiple basic residues.
• To improve the separation and identification of different phosphopeptide classes.
• To identify novel targets of basophilic kinases.

Main Methods:

• A two-dimensional strong cation exchange (SCX) chromatography strategy was employed.
• The method operates at two different acidic pHs to separate phosphopeptides.
• Enrichment is based on the charge difference of phosphorylated peptides under acidic conditions.

Main Results:

• The tandem SCX approach successfully enriched phosphopeptides with multiple basic residues.
• Over 10,000 unique "basic" phosphopeptides were identified from a modest amount of human cells.
• Many identified phosphopeptides are putative targets of basophilic kinases.

Conclusions:

• The developed method is effective for enriching under-represented phosphopeptide classes.
• This approach significantly expands the landscape of identified phosphopeptides.
• The findings provide valuable insights into basophilic kinase signaling pathways.