The three-dimensional structure of bovine odorant binding protein and its mechanism of odor recognition

Abstract

Odorant binding protein (OBP) is the major odorant binding component of mammalian nasal mucosa. The two structures of bovine OBP reported in this paper (one crystallized as purified and one soaked in the presence of a selenium-containing odorant) show that: (i) the OBP dimer is composed of two compact domains related by an approximate two-fold axis of symmetry; (ii) between residues 122 and 123 the polypeptide chains cross from one domain to the other such that each domain is formed by residues from both monomers; (iii) purified OBP already contains two bound odorant molecules (one per monomer)-odorant binding occurs by replacement of these molecules with the added odorant; and (iv) the structure of the odorant binding site can explain OBP's extraordinarily broad odorant specificity.

Nasal pungency and odor of homologous aldehydes and carboxylic acids

“…Perhaps the olfactory mucosa has a way to "focus" molecules into an area in such a way as to increase regional signal-to-noise ratio. Some investigators have speculated that odorant-binding proteins, which may transport molecules of odorant to the receptors, might provide the mechanism for such regional focusing (Bianchet et al 1996). …”

Insights into the Biosynthesis and Assembly of Cryptophycean Phycobiliproteins

“…Members of this widely distributed superfamily are known to bind small, hydrophobic molecules in the barrel interior (15,64). For instance, they are involved in diverse transport and signal transduction processes and serve as a protein matrix for pheromones or coloring substances (65,66).…”

Crystal Structure of the Allergen Equ c 1

“…3). In mMUP, the dimer interface includes the ␤-sheet composed of strands B, C, and D, and two Cd 2ϩ ions (9), whereas bovine ␤-lactoglobulin dimerizes by joining the first ␤ strand and the L1 loop of each monomer (17), and dimerization of the odorant-binding protein involves the swapping of the ␣-helix between the two monomers (7,8).…”

“…Although members of this family display low sequence similarity (often lower than 20% of amino acid identities), all share a conserved folding pattern, an 8-stranded ␤-barrel flanked by an ␣-helix at the C-terminal end of the polypeptide chain. The lipocalin ␤-barrel often defines a central apolar cavity that serves for the binding and transport of small hydrophobic molecules such as retinol (retinol-binding protein (5,6)), odorant molecules (bovine odorant-binding protein (7,8)), or pheromones (mouse major urinary protein, mMUP 1 (9), and rat urinary ␣2-globulin (10)). Several lipocalins have been described as allergenic proteins, among which the mouse major urinary protein mMUP (11), rat urinary ␣2-globulin rat urinary ␣2-globulin (12), bovine ␤-lactoglobulin (13), cockroach allergen Bla g 4 (14), dog allergens Can f 1 and Can f 2 (15), and bovine allergen Bos d 2 (16).…”