Dye-pair reporter systems for protein-peptide molecular interactions

Area of Science:

• Biochemistry
• Chemical Biology
• Analytical Chemistry

Background:

• Fluorescent dye modification of peptides enables signaling of protein interactions.
• Previous methods utilized fluorescein and tetramethylrhodamine dye pairs.
• This study explores using two tetramethylrhodamine molecules as a dye pair.

Purpose of the Study:

• To investigate the use of dual tetramethylrhodamine labeling for peptide-protein interaction assays.
• To demonstrate that dye self-affinity, driven by hydrophobicity, causes dimerization and fluorescence quenching.
• To validate the assay's effectiveness in detecting antibody-peptide and SH2 domain-phosphopeptide binding.

Main Methods:

• Synthesizing doubly dye-tagged peptides with tetramethylrhodamine or fluorescein/tetramethylrhodamine.
• Analyzing peptide-dye interactions using absorption spectroscopy to confirm dye dimerization.
• Measuring fluorescence changes upon disruption of dye dimers due to protein binding or solvent addition (acetonitrile).
• Performing fluorometric assays for specific peptide-protein interactions, including antibody-collagen peptide and SH2 domain-phosphopeptide binding.

Main Results:

• Dual tetramethylrhodamine-labeled peptides exhibited absorption spectra consistent with dye dimers.
• Disruption of dye dimers by acetonitrile or protein binding led to a 3-15 fold increase in fluorescence.
• The assay successfully detected binding of a monoclonal antibody to a type II collagen peptide (up to 4-fold fluorescence increase).
• Binding of an SH2 domain to a phosphopeptide was also detected via fluorescence changes.

Conclusions:

• Dual dye-tagging, particularly with tetramethylrhodamine, provides a robust method for peptide-protein interaction analysis.
• Dye dimerization in aqueous solution is primarily driven by hydrophobic interactions.
• This approach offers a direct, sensitive, and solution-phase assay for studying peptide-protein binding events.