Photo-affinity pulling down of low-affinity binding proteins mediated by post-translational modifications

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• Weak and transient protein-protein interactions (PPIs) mediated by post-translational modifications (PTMs) are critical in biological processes.
• Investigating PTM-mediated PPIs presents significant technical challenges, hindering research progress.

Purpose of the Study:

• To develop a novel photo-affinity pull-down assay for efficiently screening PTM-mediated PPIs.
• To overcome limitations of traditional methods in capturing low-affinity binding proteins.

Main Methods:

• Development of photo-affinity magnetic beads (PAMBs) with a PEG passivation layer.
• Utilizing photo-activated linkage to convert transient non-covalent PTM-mediated interactions into stable covalent bonds.
• Application of the assay to identify proteins interacting with a specific methylation site on Flap Endonuclease 1 (FEN1).

Main Results:

• The PAMB assay successfully captured low-affinity binding proteins, enabling the screening of PTM-mediated PPIs.
• Significant reduction in non-specific interactions (over 80%) compared to traditional pull-down assays.
• Identification of proteins interacting with a specific methylation site on FEN1, revealing more protein sub-classes.

Conclusions:

• The developed photo-affinity pull-down assay is a valuable tool for studying weak and transient PTM-mediated PPIs.
• This method enhances specificity and resolution, facilitating the discovery of potential biomedical targets.
• The assay provides a new avenue for understanding fundamental biological interactions crucial for biomedical research.