|Gene:||RBP1||Accession Number: HS03740 (MetaCyc)|
Synonyms: CRBP1, cellular retinol-binding protein, cellular retinol-binding protein I, CRBP, CRBP-I, retinol-binding protein 1
Species: Homo sapiens
Plasma retinol-binding protein (RBPs) and cellular retinol-binding proteins (CRBPs) are specific carriers of the alcohol form of vitamin A (retinol) in body fluids and within the cell, respectively. The sequestration of retinol inside a high-affinity binding-protein draws retinol into the cell and protects it from unfettered metabolism, while still allowing the formation of retinyl esters [Newcomer98, Cowan93]. LRAT, the enzyme that forms retinyl-esters, can access retinol when it is bound to CRBP1 [Yost88, MacDonald88].
The CRBPs are monomeric proteins of approximately 15.5 kDa belonging to a superfamily of small cytoplasmic proteins that specifically interact with hydrophobic ligands. Two such proteins (CRBP I and CRBP II) with distinct tissue distributions and retinoid-binding properties have been recognized in mammals.
The human CRBP I is expressed at high levels in many tissues, including ovary, adrenal and pituitary glands, and testis [Ong86], while CRBP II is confined essentially to the small intestine. In addition, the Kd of the retinol-CRBP I complex is as low as 0.1 nM [Malpeli95], whereas the binding of retinol to CRBP II is ~100-fold weaker [Li91].
The very high-affinity retinol binding-protein, holo-CRBP1, represents the major physiological form of intracellular retinol. Apo-CRBP1 interacts with enzymes to signal that the intracellular concentration of retinol is low and stimulate the hydrolysis of retinyl-esters [Boerman91, Napoli11]. The total CRBP1 concentration remains steady even when vitamin A status varies.
|Map Position: [140,065,306 <- 140,087,521]|
Molecular Weight of Polypeptide: 14.8 kD (experimental) [Ong82 ]
Relationship Links: InterPro:IN-FAMILY:IPR000463 , InterPro:IN-FAMILY:IPR000566 , InterPro:IN-FAMILY:IPR011038 , InterPro:IN-FAMILY:IPR012674 , Pfam:IN-FAMILY:PF00061 , Prints:IN-FAMILY:PR00178 , Prosite:IN-FAMILY:PS00214
Reactions known to consume the compound:
retinoate biosynthesis I
retinoate biosynthesis II
the visual cycle I (vertebrates)
all-trans-retinol + a cellular-retinol-binding protein → an all-trans retinol-[cellular-retinol-binding-protein]
a retinoid-binding protein + (3R)-11-cis-3-hydroxyretinal → a (3R)-11-cis-3-hydroxyretinal-[retinoid-binding protein]
a retinoid-binding protein + (3R)-all-trans-3-hydroxyretinal → a (3R)-all-trans-3-hydroxyretinal-[retinoid-binding protein]
Reactions known to produce the compound:
the visual cycle I (vertebrates)
an all-trans retinol-[cellular-retinol-binding-protein] + a phosphatidylcholine → a cellular-retinol-binding protein + an all-trans-retinyl ester + a 2-acyl 1-lyso-phosphatidylcholine
|Biological Process:||GO:0006776 - vitamin A metabolic process
GO:0006810 - transport
|Molecular Function:||GO:0005215 - transporter activity
GO:0005501 - retinoid binding
GO:0008289 - lipid binding
GO:0019841 - retinol binding
Enzymatic reaction of: cellular retinol-binding protein
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.
The reaction is favored in the direction shown.
Colantuoni85: Colantuoni V, Cortese R, Nilsson M, Lundvall J, Bavik CO, Eriksson U, Peterson PA, Sundelin J (1985). "Cloning and sequencing of a full length cDNA corresponding to human cellular retinol-binding protein." Biochem Biophys Res Commun 130(1);431-9. PMID: 2992469
Cowan93: Cowan SW, Newcomer ME, Jones TA (1993). "Crystallographic studies on a family of cellular lipophilic transport proteins. Refinement of P2 myelin protein and the structure determination and refinement of cellular retinol-binding protein in complex with all-trans-retinol." J Mol Biol 230(4);1225-46. PMID: 7683727
De98: De Baere E, Speleman F, Van Roy N, De Paepe A, Messiaen L (1998). "Assignment of the cellular retinol-binding protein 1 gene (RBP1) and of the coatomer beta subunit gene (COPB2) to human chromosome band 3q23 by in situ hybridization." Cytogenet Cell Genet 82(3-4);226-7. PMID: 9858824
Li91: Li E, Qian SJ, Winter NS, d'Avignon A, Levin MS, Gordon JI (1991). "Fluorine nuclear magnetic resonance analysis of the ligand binding properties of two homologous rat cellular retinol-binding proteins expressed in Escherichia coli." J Biol Chem 266(6);3622-9. PMID: 1995621
Sherman87: Sherman DR, Lloyd RS, Chytil F (1987). "Rat cellular retinol-binding protein: cDNA sequence and rapid retinol-dependent accumulation of mRNA." Proc Natl Acad Sci U S A 84(10);3209-13. PMID: 3472205
Wei87: Wei LN, Mertz JR, Goodman DS, Nguyen-Huu MC (1987). "Cellular retinoic acid- and cellular retinol-binding proteins: complementary deoxyribonucleic acid cloning, chromosomal assignment, and tissue specific expression." Mol Endocrinol 1(8);526-34. PMID: 2856408
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