Quantitative analysis of pheromone-binding protein specificity.

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Ecology

Background:

• Pheromones often exhibit low water solubility, complicating binding assays.
• Quantitative binding measurements for pheromone-binding proteins (PBPs) require robust methodologies.

Purpose of the Study:

• To develop a novel method for determining thermodynamically valid dissociation constants for ligands binding to PBPs.
• To apply this method to the Drosophila odorant-binding protein LUSH and its pheromone 11-cis vaccenyl acetate (cVA).

Main Methods:

• Utilized β-cyclodextrin as a solubilizer and transfer agent.
• Assessed LUSH refolding via N-phenyl-1-naphthylamine (NPN) binding and Förster resonance energy transfer.
• Measured cVA binding through quenching of LUSH tryptophan 123 (W123) fluorescence.
• Employed a linked equilibria model to determine equilibrium constants.

Main Results:

• Determined the LUSH-cVA dissociation constant to be approximately 100 nM.
• Quantified dissociation constants for other ligands: ~200 nM for bombykol and ~90 nM for methyl oleate.
• Demonstrated LUSH's capacity to bind diverse ligands with high affinity.

Conclusions:

• The developed method successfully quantifies ligand-PBP interactions, overcoming solubility challenges.
• LUSH exhibits broad ligand-binding capabilities, consistent with models of pheromone reception.
• This research provides valuable insights into insect olfactory mechanisms and PBP function.