Odorant binding proteins (OBPs) are small (around 14 kDa) soluble proteins isolated from the sensory organs of a wide range of insect species. OBP reversely bind odorants with dissociation constants in the micromolar range and are good candidate for transporting hydrophobic odorant molecules to olfactory receptors, through the aqueous sensillar lymph. In the genome of Drosophila melanogaster, 52 OBPs with high sequence divergence have been identified. Amongst them, OBP28a is one of the most abundant odorant binding proteins suggesting an important physiological role. A recent study proposed a novel role for this OBP in buffering changes in the odor environment (Larter et al., 2016). To further unravel and decipher the physiological role of this OBP, we investigated the ligand binding and physicochemical characterization of the recombinant OBP28. We report the heterologous secretion of OBP28a using the yeast Pichia Pastoris. The purified OBP28a was characterized using mass spectrometry, circular dicroism and gel filtration coupled to multi-angle static light scattering. We found that OBP28a is monomeric with the expected secondary structure content. Using N-phenyl naphtylamine as competitive fluorescent probe, OBP28a was shown to bind a family of attractive floral-like chemical compounds with micro-molar affinities. These results pave the way for three-dimensional investigations, experiments made feasible by the large amount of recombinant protein produced, with the aim of clearly defining the relationships between the structure and function of this drosophila OBP. Larter NK, Sun JS, Carlson JR. Organization and function of Drosophila odorant binding proteins. Elife. 2016 Nov 15;5. pii: e20242.