Disease relevance of Rbp1

• Characterization of rat cellular retinol-binding protein II expressed in Escherichia coli [1].
• Consequently, the increase in CRBP occurred only with tumor appearance and not with the general hyperplasia of the crypts caused by DMH administration [2].
• However, the adenocarcinomas had high levels of CRBP (300 to 500 pmol/g), and these levels were dramatically higher than levels of CRBP in adjacent mucosa of the same animal (40 to 100 pmol/g), colorectal mucosa from normal rats (20 pmol/g), or colorectal mucosa from rats chronically treated with DMH (22 to 25 pmol/g) [2].
• To determine if retinol acts at the beta-cell level, we assayed beta-cells of the rat insulinoma (RINm5F) line for cytosolic retinol- and retinoic acid-binding proteins (CRBP and CRABP) by radioimmunoassay (RIA) and [3H]retinol and [3H]retinoic acid binding to cytosol extracts [3].
• CRBP I and CRABP I gene expression have been examined in the oviduct, ovary, uterus, and particularly in the cervix, which normally undergoes a cyclical squamous metaplasia during the estrus cycle [4].

High impact information on Rbp1

• Specificity of cellular retinol-binding protein for compounds with vitamin A activity [5].
• Interaction of the retinol/cellular retinol-binding protein complex with isolated nuclei and nuclear components [6].
• We now report that pure CRBP delivers retinol to the specific nuclear binding sites without itself remaining bound [6].
• Localization of cellular retinol-binding protein and retinol-binding protein in cells comprising the blood-brain barrier of rat and human [7].
• The deduced amino acid sequence is identical with that of rat CRBP [8].

Chemical compound and disease context of Rbp1

• Nuclear magnetic resonance studies of 6-fluorotryptophan-substituted rat cellular retinol-binding protein II produced in Escherichia coli. Analysis of the apoprotein and the holoprotein containing bound all-trans-retinol and all-trans-retinal [9].
• 19F nuclear magnetic resonance studies of 6-fluorotryptophan-substituted rat cellular retinol binding protein II produced in Escherichia coli. An analysis of four tryptophan substitution mutants and their interactions with all-trans-retinol [10].

Biological context of Rbp1

• 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 [11].
• The nucleotide sequence shows 90.5% similarity with the human CRBP cDNA sequence [8].
• 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 [12].
• Gene expression of retinoic acid receptors, retinoid-X receptors, and cellular retinol-binding protein I in bone and its regulation by vitamin A [13].
• Comparative 19F-NMR studies of fluororetinol analogs with rat cellular retinol binding protein II (CRBP II) and rat cellular retinol-binding protein (CRBP) were performed to probe differences in the binding interactions of these two homologous proteins [14].

Anatomical context of Rbp1

• These differences in conformational flexibility likely contribute to differences in how CRBP I and CRBP II interact with ligands, membranes and retinoid metabolizing enzymes [11].
• The columnar epithelial cells of the jejunum and the cells of the proximal tubuli also exhibit high concentrations of cellular retinol-binding protein [15].
• The data indicate further that the distribution of retinol between RBP in blood and CRBP in cytosol is at equilibrium and that intracellular levels of retinol are regulated by the levels of CRBP [16].
• Unsaturated fatty acids regulate gene expression of cellular retinol-binding protein, type II in rat jejunum [17].
• Transcriptional regulation of cellular retinol-binding protein, type II gene expression in small intestine by dietary fat [18].

Associations of Rbp1 with chemical compounds

• Thus binding of retinol markedly reduced conformational flexibility in both CRBP I and CRBP II on the micro- to millisecond timescale [11].
• 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 [11].
• Finally, when retinol-deficient rats are fed retinyl acetate for 4 hr, about 4-fold accumulation of CRBP-specific mRNA is observed in the lungs [8].
• The primary structure of rat liver CRBP was elucidated by analyses of cyanogen bromide fragments and peptides obtained by tryptic and thermolytic digestions [19].
• Both polypeptides contain reactive thiol groups, but the rate of disruption of CRBP II-retinol complexes by p-chloromercuribenzoate is greater than that of CRBP-retinol [20].

Physical interactions of Rbp1

• The amounts of cellular retinol binding protein and retinoic acid binding protein in testes, as determined by sucrose gradient centrifugation, were found to be similar for retinol depleted and pair fed control rats [21].
• Retinyl methyl ether (RME) which prevents cancers of the rat mammary gland, binds to cellular retinol-binding protein and serum retinol-binding protein but not to cellular retinoic acid-binding protein or to the nuclear retinoid receptors, RARs/RXRs [22].

Other interactions of Rbp1

• The solution structure and dynamics of CRBP I and CRBP II were compared by multidimensional NMR techniques [11].
• Among cellular retinol-binding protein I (CRBP-I) and CRBP-II and cellular retinoic acid-binding protein I and II, only the CRBP-I gene was expressed [13].
• We have reported that dietary long-chain triacylglycerols (LCT) enhance the transcription of cellular retinol-binding protein, the type II (CRBPII) gene, and the liver-type fatty acid-binding protein (L-FABP) gene in the small intestine [23].
• This retinal dehydrogenase was not feedback-inhibited by all-trans- or 9-cis-retinoic acid, nor by holocellular retinoic acid-binding protein, but was stimulated modestly by apocellular retinoic acid-binding protein, an effect not observed in the presence of cellular retinol-binding protein [24].
• When the cellular retinol-binding protein was partially purified from rat testes, it exhibited fluorescence excitation and emission spectra similar to that of all-trans-retinol in hexane [21].

Analytical, diagnostic and therapeutic context of Rbp1

• In addition, a sensitive radioimmunoassay was developed to quantitate cellular retinol-binding protein in various tissues [15].
• Alteration of the binding specificity of cellular retinol-binding protein II by site-directed mutagenesis [25].
• Crystallization of rat cellular retinol binding protein II. Preliminary X-ray data obtained from the apoprotein expressed in Escherichia coli [26].
• These results demonstrate that the 1,25-dihydroxyvitamin D3 modulated protein in chick embryonic organ culture is chick CRBP II [27].
• Total RNA was isolated from inguinal, dorsal, mesenteric, epididymal, perinephric, and brown adipose tissue, and average RBP and CRBP mRNA levels were determined by Northern blot analysis [28].

References