Crystal structure of the human odorant binding protein, OBP IIa

Human odorant‐binding protein, OBP IIa , is expressed by nasal epithelia to facilitate transport of hydrophobic odorant molecules across the aqueous mucus. Here, we report its crystallographic analysis at 2.6 Å resolution. OBP IIa is a monomeric protein that exhibits the classical lipocalin fold with a conserved eight‐stranded β‐barrel harboring a remarkably large hydrophobic pocket. Basic residues within the four loops that shape the entrance to this ligand‐binding site evoke a positive electrostatic potential. Human OBP IIa shows distinct features compared with other mammalian OBPs, including a potentially reactive Cys side chain within its pocket similar to human tear lipocalin. Proteins 2015; 83:1180–1184. © 2015 Wiley Periodicals, Inc.