The structure of the monomeric porcine odorant binding protein sheds light on the domain swapping mechanism.
The X-ray structure of the porcine odorant binding protein (OBPp) was determined at 2.25 A resolution. This lipocalin is a monomer and is devoid of naturally occurring bound ligand, contrary to what was observed in the case of bovine OBP [Tegoni, M., et al. (1996) Nat. Struct. Biol. 3, 863-867; Bianchet, M. A., et al. (1996) Nat. Struct. Biol. 3, 934-939]. In this latter protein, a dimer without any disulfide bridges, domain swapping was found to occur between the beta- and alpha-domains. A single Gly (121) insertion was found in OBPp when it was compared to OBPb, which may prevent domain swapping from taking place. The presence of a disulfide bridge between the OBPp beta- and alpha-domains (cysteines 63 and 155) may lock the resulting fold in a nonswapped monomeric conformation. Comparisons with other OBPs indicate that the two cysteines involved in the OBPp disulfide bridge are conserved in the sequence, suggesting that OBPp may be considered a prototypic OBP fold, and not OBPb.
Spinelli
S
S
Architecture et Fonction des Macromolécules Biologiques, UPR 9039, CNRS, IFR1, Marseille, France.
Ramoni
R
R
Grolli
S
S
Bonicel
J
J
Cambillau
C
C
Tegoni
M
M
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D018360:Crystallography, X-Ray; D019281:Dimerization; D005998:Glycine / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009297:Nasal Mucosa / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D018035:Receptors, Odorant / Q000737:chemistry* / Q000378:metabolism; D013329:Structure-Activity Relationship; D013552:Swine
D018035:Receptors, Odorant; C045648:odorant-binding protein; D005998:Glycine