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PDBsum entry 1j7x
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Transport protein
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PDB id
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1j7x
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Crystal structure of the functional unit of interphotoreceptor retinoid binding protein.
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Authors
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A.Loew,
F.Gonzalez-Fernandez.
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Ref.
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Structure, 2002,
10,
43-49.
[DOI no: ]
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PubMed id
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Abstract
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Interphotoreceptor retinoid binding protein (IRBP), the major soluble component
of the interphotoreceptor matrix, is critical to the function, integrity, and
development of the vertebrate retina. Although its role is poorly understood,
IRBP has been thought to protect 11-cis retinal and all-trans retinol while
facilitating their exchange between the photoreceptors and retinal-pigmented
epithelium. We determined the X-ray structure of one of the functional units, or
modules, of Xenopus laevis IRBP to 1.8 A resolution by multiwavelength anomalous
dispersion. The monomeric protein consists of two domains separated by a
hydrophobic ligand binding site. A structural homology to the recently solved
photosystem II D1 C-terminal-processing protease and the enoyl-CoA
isomerase/hydratase family suggests the utility of a common fold used in diverse
settings, ranging from proteolysis to fatty acid isomerization to retinoid
transport.
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Figure 3.
Figure 3. Putative Ligand Binding Sites of X2IRBP(A) Ribbon
stereo diagram of X2IRBP (shown in yellow) superposed with
2-enoyl-CoA hydratase (blue) in complex with octanoyl-CoA (red).
The bound ligand of 2-enoyl-CoA hydratase was transferred from
the 2-enoyl-CoA hydratase/octanoyl-CoA structure to the
equivalent position in X2IRBP. The fatty acid portion of the
ligand binds to the hydrophobic site 1, as identified in Figure
3b.(B) Hydrophobicity surface representation, where white
represents high hydrophobicity and blue high hydrophilicity. The
arrowhead identifies a shallow hydrophobic binding cleft between
domains A and B, the putative first binding site (site 1). The
arrow identifies a cavity located in a hydrophobic patch that
leads to the potential second binding site (site 2).
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The above figure is
reprinted
by permission from Cell Press:
Structure
(2002,
10,
43-49)
copyright 2002.
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