1cbi
From Proteopedia
|
APO-CELLULAR RETINOIC ACID BINDING PROTEIN I
Overview
A recombinant form of murine apo-cellular retinoic acid binding protein I, (apo-CRABPI) has been purified and crystallized at pH 5.0, and the crystal, structure has been refined to an R-factor of 19.6% at a resolution of 2.7, A. CRABPI binds all-trans retinoic acid and some retinoic acid metabolites, with nanomolar affinities. Coordinates of the holo form of CRABP were not, available during the early stages of the study, and in spite of numerous, homologs of known structure, phases were not obtainable through molecular, replacement. Instead, an interpretable electron density map was obtained, by multiple isomorphous replacement methods after improvement of the, heavy-atom parameters with density modified trial phases. Two molecules of, apo-CRABPI occupy the P3121 asymmetric unit and are related by pseudo, 2-fold rotational symmetry. Unique conformational differences are apparent, between the two molecules. In all of the family members studied to date, there is a lack of hydrogen bonds between two of the component, beta-strands resulting in a gap in the interstand hydrogen bonding, pattern. In the crystallographic dimer described here, a continuous, intermolecular beta-sheet is formed by using this gap region. This is, possible because of an 8 A outward maximum displacement of the tight turn, between the third and fourth beta-strands on one of the molecules. The, result is a double beta-barrel containing two apo-CRABPI molecules with a, more open, ligand-accessible binding cavity, which has not been observed, in other structures of a family of proteins that bind hydrophobic ligands.
About this Structure
1CBI is a Single protein structure of sequence from Mus musculus. Full crystallographic information is available from OCA.
Reference
Crystal structure of cellular retinoic acid binding protein I shows increased access to the binding cavity due to formation of an intermolecular beta-sheet., Thompson JR, Bratt JM, Banaszak LJ, J Mol Biol. 1995 Sep 29;252(4):433-46. PMID:7563063
Page seeded by OCA on Tue Nov 20 12:19:14 2007
