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Sequence-dependent enrichment of a model phosphopeptide: a combined MALDI-TOF and NMR study
Lucrèce Matheron1, Matheron Lucrèce, Emmanuelle Sachon
1Université P. et M. Curie Paris 6, UMR 7203 CNRS-UPMC-ENS, 4, Place Jussieu, 75005 Paris, Ecole Normale Supérieure, Département de Chimie, 24, rue Lhomond, 75005 Paris, France.
Abstract:
The goal of this study was to detect and quantify by MALDI-TOF MS the phosphorylation of a peptide containing the recognition motif of the Protein Kinase C (PKC). Such model peptide can be used as a phosphorylation probe to follow intracellular kinase/phosphatase activities. This study allowed us to establish relationships between sequence specificities and affinity for TiO(2) or IMAC media. The peptide has the sequence biotin-GGGGCFRTPSFLKK-NH(2) in which the serine residue can be phosphorylated. Enrichment of the corresponding phosphopeptide, by the dedicated IMAC and TiO(2) affinity chromatography methods, proved inefficient. By combining MALDI-TOF and NMR data, we first showed that the lack of affinity of the phosphopeptide for TiO(2) was partly related to the basic property of its peptide sequence. Furthermore, the peptide shows local structuration around the P(9)- S(10) segment, with formation of a salt bridge between the guanidinium group of the R(7) side chain and the phosphate moiety. In conjunction with an inadequate position of the {biotin-G(4)} N-terminal tag, this local structure could shield the phosphate group, preventing interaction with TiO(2). To improve TiO(2) affinity, the peptide sequence was modified accordingly. The new sequences retained the biological properties while their enrichment by IMAC or TiO(2) became possible.
Insights
This study optimized phosphopeptide enrichment using TiO(2) and IMAC chromatography. Modified peptide sequences improved affinity, enabling efficient detection of phosphorylated Protein Kinase C (PKC) motifs.
Area of Science:
- Biochemistry
- Analytical Chemistry
- Proteomics
Background:
- Protein phosphorylation is crucial for cellular signaling, regulated by kinases and phosphatases.
- Developing sensitive probes for intracellular kinase/phosphatase activity is essential.
- Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) is a key analytical technique.
Purpose of the Study:
- To detect and quantify phosphorylation of a model peptide using MALDI-TOF MS.
- To investigate the affinity of a phosphopeptide for TiO(2) and Immobilized Metal Affinity Chromatography (IMAC) media.
- To establish relationships between peptide sequence, structure, and affinity for enrichment media.
Main Methods:
- Utilized MALDI-TOF MS for peptide phosphorylation detection and quantification.
- Employed TiO(2) and IMAC affinity chromatography for phosphopeptide enrichment.
- Combined MALDI-TOF MS and Nuclear Magnetic Resonance (NMR) for structural analysis.
Main Results:
- Initial enrichment of the phosphopeptide using TiO(2) and IMAC was inefficient.
- MALDI-TOF MS and NMR revealed that phosphopeptide affinity for TiO(2) was hindered by its basic sequence and local structuration, including a salt bridge shielding the phosphate group.
- Sequence modification successfully improved TiO(2) and IMAC affinity, enabling efficient enrichment.
Conclusions:
- Peptide sequence and local structure significantly impact phosphopeptide affinity for enrichment media.
- Optimized peptide sequences facilitate efficient phosphopeptide enrichment via TiO(2) and IMAC chromatography.
- This work provides a foundation for developing improved phosphorylation probes for kinase/phosphatase activity monitoring.
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