 |
PDBsum entry 1hqp
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Signaling protein
|
PDB id
|
|
|
|
1hqp
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Crystal structure of a truncated form of porcine odorant-Binding protein.
|
|
|
Authors
|
|
M.Perduca,
F.Mancia,
R.Del giorgio,
H.L.Monaco.
|
|
|
Ref.
|
|
Proteins, 2001,
42,
201-209.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The odorant-binding proteins (OBPs) are a family of structurally related
molecules that are found in high concentrations in the nasal mucus of
vertebrates and bind with moderate affinity a large family of hydrophobic
odorants. On the basis of their quaternary structure, the OBPs have been
classified as monomers, homodimers, and heterodimers. Porcine OBP was believed
for a long time to be a monomer under physiological conditions but there are
recent data that support the existence of a monomer-dimer equilibrium. We have
determined the crystal structure of a monoclinic form of porcine OBP and found
that the truncated molecules, which lack the first 8 amino acids, pack in the
cell as dimers that appear to have physiological relevance. The presence in the
maps of electron density for an endogenous ligand has also let us identify the
side chain of the amino acids that are at the ligand-binding site. In addition,
an alternative way of access to the central cavity that binds the ligands is
suggested by the particular packing of the molecules in this unit cell. Proteins
2001;42:201-209.
|
|
|
|
|
|
|
|
Figure 5.
Figure 5. a: The residual electron density in the cavity of the
porcine OBP molecule. Represented is a 2 Fobs-Fc map calculated
with phases from the final protein model contoured at a 1  level.
Only the 4 amino acids that have density clearly present in this
section are represented. b: The position of the endogenous
ligand in the internal cavity of the porcine OBP molecule. The
ligand is modelled by the canonical odorant
2-isobutyl-3-methoxypyrazine.
|
|
Figure 6.
Figure 6. The crystallographic dimer with the bottom monomer
replaced by an RBP molecule in approximately the same position
and orientation. The retinol ligand is visible with the hydroxyl
group on the molecular surface. Notice the position of the loops
at the entrance of the central cavity in RBP and the equivalent
loops in the porcine OBP molecule.
|
|
|
|
|
|
The above figures are
reprinted
by permission from John Wiley & Sons, Inc.:
Proteins
(2001,
42,
201-209)
copyright 2001.
|
|
|
|
|
|
|
