PROBING SITE-SPECIFIC INTERACTIONS BETWEEN EPIDERMAL GROWTH FACTOR RECEPTOR AND AN ADNECTIN USING HDX-ETD MS APPROACH

Importance of the Topic

EGFR is a central regulator of cellular proliferation and a validated target in oncology. Precise mapping of its interaction sites with therapeutic binders such as adnectins supports rational drug design and enhances understanding of receptor modulation.

Study Objectives and Overview

This work aimed to combine hydrogen/deuterium exchange mass spectrometry (HDX-MS) with targeted electron transfer dissociation (ETD) to achieve residue-level characterization of the EGFR/adnectin binding interface. By comparing deuterium uptake in unbound and adnectin-bound EGFR, key contact sites were identified.

Materials and Methods

Samples of human EGFR and anti-EGFR adnectin were prepared at 6.7 and 2.3 mg/mL, respectively, mixed in a 1:2 ratio and incubated 30 min at room temperature. Deuterium labeling was performed in PBS/D₂O at pH 7.2 for 1 h (peptide level) and 30 min (residue level). Reactions were quenched at pH 2.4, followed by online pepsin digestion at 25 °C and rapid reversed-phase UPLC separation at 0 °C. Both CID and targeted ETD fragmentation were employed, with triplicate runs for statistical robustness.

Instrumentation

The HDX workflow utilized a Waters nanoACQUITY UPLC system with HDX technology and a Waters Synapt G2-S mass spectrometer equipped with an ETD front-end. The ETD reaction cell was implemented in the triwave trap, and 1,3-dicyanobenzene served as the reagent. Data were processed using Waters ProteinLynx Global Server and DynamX 3.0 software.

Key Results and Discussion

Peptide-level HDX identified three EGFR regions (residues 1–19, 46–53, 96–108) showing significant protection upon adnectin binding. Targeted ETD fragmentation of the 1–19 peptide enabled deuterium localization to individual amide bonds. Residues T15, Q16, L17 and G18 exhibited reduced uptake in the bound state, confirming the crystallographic interface. Additionally, K13 and L14 displayed partial protection, suggesting an extended epitope beyond the X-ray model.

Benefits and Practical Applications

• High-resolution mapping of protein–protein interfaces at single-residue level.
• Rapid epitope localization complementing structural biology techniques.
• Valuable for guiding therapeutic protein engineering and optimizing binding affinity.

Future Trends and Applications

Advances in HDX-ETD instrumentation and data analysis will broaden its use in drug discovery, enabling dynamic interface characterization in larger complexes. Integration with computational modeling may predict binding energetics and guide rational design of next-generation biologics.

Conclusion

The combined HDX-MS and ETD approach delivers site-specific insights into EGFR/adnectin interactions, validating known contact residues and revealing novel interface contributions. This methodology represents a powerful tool for detailed structural analysis of therapeutic protein complexes.

References

• Rand et al. Journal of the American Society for Mass Spectrometry, 2011, 22:1784–1793.
• Rand et al. Analytical Chemistry, 2009, 81:5577–5584.
• Ramamurthy et al. Structure, 2012, 20:259–269.