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NMR SOLUTION STRUCTURE OF HUMAN CELLULAR RETINOIC ACID BINDING PROTEIN-TYPE II, 22 STRUCTURES

Overview

The structure of human apo-cellular retinoic acid binding protein II, (apo-CRABPII) in solution at pH 7.3 has been determined by NMR, spectroscopy. The sequential assignments of the 1H, 13C, and 15N, resonances of apo-CRABPII were established by multinuclear, multidimensional NMR spectroscopy. The solution structure of apo-CRABPII, was derived from 2382 experimental NMR restraints using a hybrid distance, geometry-simulated annealing protocol. The root-mean-square deviation of, the ensemble of 25 refined conformers that represent the structure from, the mean coordinate set derived from them was 0.54 +/- 0.18 and 0.92 +/-, 0.20 A for the backbone atoms and all heavy atoms, respectively, of all, residues except Ala32-Pro39 and Thr57-Glu62, which are in disordered, regions. The solution structure of apo-CRABPII is similar to the crystal, structure of holo-CRABPII [Kleywegt, G. J., Bergfors, T., Senn, H., Le, Motte, P., Gsell, B., Shudo, K., and Jones, T. A. (1994) Structure 2, 1241-1258] except the ligand entrance, which is sufficiently enlarged in, the apoprotein to be readily accessible to retinoic acid. The enlargement, of the ligand entrance of apo-CRABPII relative to that of holo-CRABPII is, due mainly to a concerted conformational change in three structural, elements, namely, the second helix, the betaC-betaD loop, and the, betaE-betaF loop. Furthermore, the ligand-binding pocket of apo-CRABPII, showed evidence of dynamic disorder; among the 21 residues that constitute, this pocket, 16 residues had weak or no detectable cross-peaks in the, two-dimensional 1H-15N HSQC spectrum recorded under conditions of minimal, water saturation or dephasing. Apo-CRABPII is largely monomeric in, solution, with no evidence for the dimeric structure shown in the crystal, structure of apo-CRABPI which was suggested to be a prerequisite for, ligand entry [Thompson, J. R., Bratt, J. M., and Banaszak, L. J. (1995) J., Mol. Biol. 252, 433-446]. Thus, the widening of the ligand entrance, required for entry of retinoic acid appears to be a property of monomeric, apo-CRABPII.

About this Structure

1BLR is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

NMR solution structure of type II human cellular retinoic acid binding protein: implications for ligand binding., Wang L, Li Y, Abildgaard F, Markley JL, Yan H, Biochemistry. 1998 Sep 15;37(37):12727-36. PMID:9737849

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