Disease relevance of RBP1

• RalDH(II) expressed in E. coli recognizes as substrates free retinal, with a Km of approximately 0.7 microM, and cellular retinol-binding protein-bound retinal, with a Km of approximately 0.2 microM [1].

High impact information on RBP1

• RalDH(II) also can utilize as substrate retinal generated in situ by microsomal retinol dehydrogenases, from the physiologically most abundant substrate: retinol bound to cellular retinol-binding protein [1].
• ApoCRBP proved to be a specific inhibitor of retinoic acid synthesis from CRBP-bound retinol [2].
• NAD-supported reactions carried out in the presence or in the absence of dimethyl sulfoxide yielded apparent Km and Vmax values for the retinol-CRBP complex of 3.5 +/- 0.6 microM, 611 +/- 49 pmol h-1 (mg of protein)-1, and 0.84 +/- 0.12 microM, 601 +/- 38 pmol h-1 (mg of protein)-1, respectively [2].
• Cytosolic retinoic acid synthesis from retinol-CRBP was strictly dependent on the exogenous supply of either NAD or NADP [2].
• Reduction of retinaldehyde bound to cellular retinol-binding protein (type II) by microsomes from rat small intestine [3].

Biological context of RBP1

• Evidence is presented that retinol bound to a plasma membrane receptor sharing functional and structural similarities with CRBP is the actual substrate for esterification [4].
• The saturation of the binding site with native ligand is 0.95 +/- 0.05 mol of retinoid/mol of protein for cellular retinol-binding protein purified from frozen and fresh retina and retinal pigment epithelium [5].
• A comparison of the complete amino acid sequences of the members of this protein family, which also includes the rat intestinal fatty acid-binding protein, shows that CRABP is more similar to cellular retinol-binding protein and protein P2 than to the fatty acid-binding proteins [6].
• This is associated with the loss of protein binding to the 5'-flanking region of the CRBP gene [7].
• Inhibition of lipid peroxidation (decrease of chemiluminescence) was observed with the addition of increasing amounts (100-600 microg) of CRBP to RPE mitochondria [8].

Anatomical context of RBP1

• All-trans-retinol is the only retinoid associated with the cellular retinol-binding protein from retina and retinal pigment epithelium [5].
• Acyl-CoA-independent esterification of retinol bound to cellular retinol-binding protein (type II) by microsomes from rat small intestine [9].
• Serum factors induce messenger ribonucleic acid levels for cellular retinol-binding protein in rat Sertoli cells [7].
• This study analyzes the effect of cellular retinol-binding protein (CRBP), partially purified from retinal pigment epithelium (RPE) cytosol, on the non-enzymatic lipid peroxidation induced by fatty acid hydroperoxides of mitochondrial membranes isolated from bovine RPE [8].
• Immunostaining of CRBP was most intense in the granulosa cells of preantral follicles and present, but diminished, in thecal and granulosa cells of antral follicles [10].

Associations of RBP1 with chemical compounds

• Cellular retinol-binding protein (type II) (CRBP(II)), a newly described retinol-binding protein, is present in the small intestinal absorptive cell at high levels [9].
• Mobilization of retinol stored as a membrane-bound retinyl-ester is mediated by a membrane-associated hydrolase activity selectively controlled by the level of apo-CRBP which acts as a carrier for the released retinol [4].
• Both the induction and degradation of CRBP mRNA were inhibited by the protein synthesis inhibitor cycloheximide [7].
• Mass spectrometric (MS) analysis of isotopically labeled retinoids showed that isomerization proceeds via alkyl cleavage mechanism, but the product of isomerization depended on the specificity of the retinoid-binding protein(s) as evidenced by the production of 13-cis-retinol in the presence of cellular retinoid-binding protein (CRBP) [11].
• The results of these and previous studies indicate that CRBP is particularly sensitive to modifications of the retinol hydroxyl end group [12].

Physical interactions of RBP1

• Eleven-cis-retinol bound to CRALBP is a better substrate for esterification by microsomes from retinal pigment epithelium (RPE) than all-trans-retinol bound to cellular retinol-binding protein (CRBP) [13].

Other interactions of RBP1

• It is distinct from both cellular retinol-binding protein and cellular retinoic acid-binding protein on the bases of binding specificity and isoelectric point [14].

Analytical, diagnostic and therapeutic context of RBP1

• To complement the absorbance measurements, the IRBP and CRBP in these mixtures were subsequently separated by size-exclusion HPLC and individually analysed for retinol content by scanning the effluent with a multiple-diode-array detector [15].
• Northern blot analysis demonstrated that thecal and granulosa cells from antral follicles and luteal tissue expressed RBP and CRBP mRNA [10].
• The interactions with retinol and retinol analogs of bovine cellular retinol-binding protein (CRBP) have been investigated, by means of fluorescence titrations, to obtain more information on the structural features of retinoid that may be required for their interaction with the binding protein [12].

References