Epitope Mapping with Diethylpyrocarbonate Covalent Labeling-Mass Spectrometry

Area of Science:

• Biochemistry
• Immunology
• Analytical Chemistry

Background:

• Antigen-antibody epitope mapping is crucial for understanding molecular interactions.
• Developing novel protein therapeutics relies on precise knowledge of binding sites.

Purpose of the Study:

• To investigate diethylpyrocarbonate (DEPC) covalent labeling coupled with mass spectrometry for analyzing antigen-antibody interactions.
• To characterize the impact of antibody binding on the labeling patterns of tumor necrosis factor alpha (TNFα).

Main Methods:

• Utilized diethylpyrocarbonate (DEPC) covalent labeling combined with mass spectrometry.
• Analyzed the well-characterized model system of TNFα in complex with three different antibodies.
• Quantified changes in DEPC labeling extent for various residues upon antibody binding.

Main Results:

• Residues buried within the epitope showed decreased DEPC labeling, as anticipated.
• Serine, threonine, and tyrosine residues at epitope edges exhibited increased labeling due to hydrophobic pocket formation.
• Distant residues generally showed no change, but some altered labeling due to microenvironment variations.

Conclusions:

• DEPC labeling is sensitive to both solvent exposure and microenvironmental changes around residues.
• Antibody binding significantly influences DEPC labeling patterns, providing insights into epitope interactions.
• This method offers a valuable approach for epitope mapping and understanding protein-protein interactions in therapeutic development.