1EPB: STRUCTURE OF THE EPIDIDYMAL RETINOIC ACID-BINDING PROTEIN AT 2.1 ANGSTROMS RESOLUTION

Citation:
Abstract
BACKGROUND: Androgen-dependent proteins in the lumen of the epididymis are required for sperm maturation. One of these is a retinoic acid binding protein, E-RABP, which binds both all-trans and 9-cis retinoic acid. The other retinoid-binding proteins whose structures are known do not bind 9-cis retinoids. RESULTS: We describe the X-ray structure determination of E-RABP with and without bound ligand. The ligand binds deep in the beta-barrel of the protein, the beta-ionone ring innermost. The binding site, like the ligand, is amphipathic and the deepest part of the cavity is formed by a ring of aromatic amino acids. The isoprene tail of all-trans retinoic acid is bound in a folded conformation which resembles that of the 9-cis isomer. CONCLUSION: E-RABP achieves high-affinity binding of both all-trans and 9-cis isomers of retinoic acid by forcing the all-trans form to bind in a folded conformation. The RAR family of nuclear receptors for retinoic acid also binds both isomers, and their binding sites may therefore be similar.
PDB ID: 1EPBDownload
MMDB ID: 870
PDB Deposition Date: 1993/6/15
Updated in MMDB: 2017/12
Experimental Method:
x-ray diffraction
Resolution: 2.2  Å
Source Organism:
Similar Structures:
Biological Unit for 1EPB: dimeric; determined by author
Molecular Components in 1EPB
Label Count Molecule
Proteins (2 molecules)
2
Epididymal Retinoic Acid-binding Protein(Gene symbol: Lcn5)
Molecule annotation
Chemicals (2 molecules)
1
2
* Click molecule labels to explore molecular sequence information.

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