title: Binding of retinol induces changes in rat cellular retinol-binding protein II conformation and backbone dynamics.
abstract: The structure and backbone dynamics of rat holo cellular retinol-binding protein II (holo-CRBP II) in solution has been determined by multidimensional NMR. The final structure ensemble was based on 3980 distance and 30 dihedral angle restraints, and was calculated using metric matrix distance geometry with pairwise Gaussian metrization followed by simulated annealing. The average RMS deviation of the backbone atoms for the final 25 structures relative to their mean coordinates is 0.85(+/-0.09) A. Comparison of the solution structure of holo-CRBP II with apo-CRBP II indicates that the protein undergoes conformational changes not previously observed in crystalline CRBP II, affecting residues 28-35 of the helix-turn-helix, residues 37-38 of the subsequent linker, as well as the beta-hairpin C-D, E-F and G-H loops. The bound retinol is completely buried inside the binding cavity and oriented as in the crystal structure. The order parameters derived from the (15)N T(1), T(2) and steady-state NOE parameters show that the backbone dynamics of holo-CRBP II is restricted throughout the polypeptide. The T(2) derived apparent backbone exchange rate and amide (1)H exchange rate both indicate that the microsecond to second timescale conformational exchange occurring in the portal region of the apo form has been suppressed in the holo form.
authors.affiliation: Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: J
authors.initials: J
authors.lastname: Lu
authors.forename: C L
authors.initials: CL
authors.lastname: Lin
authors.forename: C
authors.initials: C
authors.lastname: Tang
authors.forename: J W
authors.initials: JW
authors.lastname: Ponder
authors.forename: J L
authors.initials: JL
authors.lastname: Kao
authors.forename: D P
authors.initials: DP
authors.lastname: Cistola
authors.forename: E
authors.initials: E
authors.lastname: Li
mesh_terms: D000577:Amides / Q000378:metabolism; D000818:Animals; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D019077:Helix-Turn-Helix Motifs; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017433:Protein Structure, Secondary; D051381:Rats; D012177:Retinol-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D054840:Retinol-Binding Proteins, Cellular; D013816:Thermodynamics; D014801:Vitamin A / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000577:Amides; D001059:Apoproteins; D008024:Ligands; C518458:Rbp1 protein, rat; C518461:Rbp2 protein, rat; D012177:Retinol-Binding Proteins; D054840:Retinol-Binding Proteins, Cellular; D014801:Vitamin A; D006859:Hydrogen