Disease relevance of Rbp2

• We have now efficiently expressed rat CRBP II in E. coli [1].

High impact information on Rbp2

• The small intestine contains the highest concentrations of CRBP II mRNA in adult rats [2].
• They also support the concept that CRBP II plays a role in the intestinal absorption or esterification of retinol and suggest that changes in hepatic metabolism of vitamin A occur during development [2].
• CRBP II mRNA is first detectable in intestinal RNA during the 19th day of gestation, a time that corresponds to the appearance of an absorptive columnar epithelium [2].
• To examine whether the isomerized RAs elicit biological actions in vivo, the induction of target genes-[cellular retinol-binding protein type II (CRBP II) for 9-cis-RA and all-trans-retinoic acid receptor beta (RAR beta) for 9-cis- and all-trans-RAs] was determined [3].
• A comparative study of the interactions of rat cellular retinol-binding protein (CRBP) and cellular retinol-binding protein II (CRBP II) with a number of synthetic phenyl-substituted analogs of all-trans-retinol was performed using fluorescence and nuclear magnetic resonance analysis [4].

Chemical compound and disease context of Rbp2

• Efficient incorporation of 6-fluorotryptophan (93%) was achieved by growing a tryptophan auxotroph of E. coli harboring a prokaryotic expression vector with a full-length rat CRBP II cDNA on defined medium supplemented with the analog [5].

Biological context of Rbp2

• The structure and dynamics of rat apo-cellular retinol binding protein II (apo-CRBP II) in solution has been determined by multidimensional NMR analysis of uniformly enriched recombinant rat 13C, 15N-apo-CRBP II and 15N-apo-CRBP II [6].
• Cellular retinol-binding protein I (CRBP I) and cellular retinol-binding protein II (CRBP II) are closely homologous proteins that play distinct roles in the maintenance of vitamin A homeostasis [7].
• Results from competitive binding studies with retinol and retinal indicated that there is a much larger difference between the affinities of CRBP for retinol and retinal than between the affinities of CRBPII for these two ligands [8].
• We have genetically engineered two amino acid substitutions in CRBP II: 1) Gln109 to Arg and 2) Gln129 to Arg [9].
• Cellular retinol-binding protein (CRBP) and cellular retinol-binding protein II (CRBP II) are 132-residue cytosolic proteins which have 56% amino acid sequence identity and bind all-trans-retinol as their endogenous ligand [10].

Anatomical context of Rbp2

• These differences in conformational flexibility likely contribute to differences in how CRBP I and CRBP II interact with ligands, membranes and retinoid metabolizing enzymes [7].
• In the adult rat, expression of the CRBP II gene is essentially limited to the small intestinal lining cells (enterocytes), suggesting that CRBP II may be uniquely adapted for intestinal metabolism of newly absorbed retinol [11].
• Comparative 19F NMR studies were performed on rat cellular retinol-binding protein (CRBP) and cellular retinol-binding protein II (CRBPII) to better understand their role in intracellular retinol metabolism within the polarized absorptive epithelial cells (enterocytes) of the intestine [8].
• We have shown that cellular retinol-binding protein, type II (CRBP II) mRNA and its protein levels are elevated in the jejunum of rats fed a diet rich in long-chain triacylglycerols [12].

Associations of Rbp2 with chemical compounds

• Intraligand NOE cross-peaks were detected for the hydroxyl proton in the NOESY spectrum of CRBP I-bound retinol, but not for CRBP II-bound retinol, indicating that the conformational dynamics of retinol binding are different for these two proteins [7].
• Molecular model building, based on the crystalline structures of two homologous proteins was used to predict the positions of the 4 tryptophan residues of CRBP II and to make tentative resonance assignments [5].
• Rat cellular retinol-binding protein II (CRBP II) is an abundant 134-residue intestinal protein that binds all-trans-retinol and all-trans-retinal [9].
• Comparison of the 19F NMR spectra of 6-fluorotryptophan-substituted CRBP II with and without bound all-trans-retinol revealed that resonances corresponding to 2 tryptophan residues (designated WA and WB) undergo large downfield changes in chemical shifts (2.0 and 0.5 ppm, respectively) associated with ligand binding [5].
• Rat cellular retinol-binding protein II (CRBP II) is a 15.6-kDa intestinal protein which binds all-trans-retinol and all-trans-retinal but not all-trans-retinoic acid [5].

Physical interactions of Rbp2

• Cellular retinol-binding protein II (CRBP-II) and intestinal fatty acid-binding protein (I-FABP) are both expressed in small intestinal enterocytes and exhibit 31% sequence identity [13].

Other interactions of Rbp2

• The solution structure and dynamics of CRBP I and CRBP II were compared by multidimensional NMR techniques [7].
• X-ray diffraction data suggest that the unit cell parameters of crystalline apo-CRBP II resemble those of I-FABP [1].
• Electrophoretic mobility-shift assay revealed that both PPARalpha-RXRalpha and PPARdelta-RXRalpha heterodimers, specifically and in a dose-dependent manner, bound to the two PPRE-like elements of the rat CRBPII gene as well as the known PPREs in the L-FABP and acyl-CoA oxidase genes [14].
• These results suggest that the possible perinatal RA production by RALDHs might regulate various RA-target genes including CRBPII and RARalpha through RXRalpha or HNF-4 in the small intestine [15].

Analytical, diagnostic and therapeutic context of Rbp2

• Pulse-chase experiments in chick embryonic duodenal organ culture strongly suggest that 1,25-dihydroxyvitamin D3 markedly decreases the synthesis of CRBP II, while not changing the degradation rate [16].
• Our ability to express CRBP II in Escherichia coli and to construct individual tryptophan substitution mutants by site-directed mutagenesis has provided a useful model system for studying the fluorescence of a multi-tryptophan protein [17].
• Force-feeding a diet containing linoleic acid produced an elevation of CRBP II mRNA levels in rats in both a dose-dependent (0.053-0.21 mol/L) and time-dependent (up to 6 h) manner [12].
• Gel shift assay showed that the binding activity of rat jejunal nuclear protein to the nuclear receptor response elements located in the rat CRBPII gene (RXRE and RE3) was greater in rats fed high-fat diet than in those fed fat-free diet and were enhanced by addition of bacterially expressed PPARalpha protein [18].
• Oral administration of corn oil in the animals fed vitamin A-free diet elicited approximately threefold accumulation of CRBP II mRNA within 6 h [19].

References