F
IPR002449

Retinol binding protein/Purpurin

InterPro entry
Short nameRetinol-bd/Purpurin
Overlapping
homologous
superfamilies
 
Calycin (IPR012674)
family relationships

Description

Proteins in this family include plasma retinol binding protein (pRBP) and purpurin. They mediate retinol transport in blood plasma
[9]
. Binding to RBP allows the hydrophobic vitamin to circulate in blood, but retinol dissociates from the protein prior to entering target cells
[10]
.

Retinol circulates in the plasma without significant loss because it is bound to pRBP. This protein is synthesized primarily in the liver, where it requires the binding of retinol to trigger its secretion
[4]
. In mammals, pRBP binds to transthyretin in the plasma, preventing the loss of pRBP through glomerular filtration
[1]
. It has been suggested that a surface cell receptor would recognise the retinol-pRBP-transthyretin complex and, in that way, retinol would be delivered into the cell. However, such a protein remains to be identified. In fish, no transthyretin homologue has been found, though fish pRBP is capable of binding mammalian transthyretin
[7]
. In Cyprinus carpio, pRBP is N-glycosylated and it has been suggested that pRBP filtration through kidney glomeruli may be reduced by a glycosylation-dependent increase in the molecular size and negative charge of the protein, since kidney filtration of anionic proteins is less than half that of neutral protein of the same size
[8]
.

The role of pRBP in retinol transport enables it to fulfill a number of physiological functions:1) it facilitates the transfer of insoluble retinol between tissues, principally transport from storage sites in the liver to peripheral tissues, 2) pRBP protects bound retinol from oxidation and tissues from the indiscriminate distribution of such a biologically active molecule, 3) the synthesis of pRBP regulates retinol release from the liver and mediates the specificity of its uptake by target cells, and 4) pRBP is believed to have an important role in the transfer of retinol from maternal circulation to the developing fetus in mammals
[3]
.

Purpurin is a constituent of adherons, high molecular weight glycoprotein complexes that are released into the growth medium of cultured cells. Adherons mediate the adhesive interactions of many cell types, including those of embryonic chick neural retina. Purpurin promotes cell-adheron adhesion by interacting with a cell surface heparan sulphate proteoglycan. It also prolongs the survival of cultured neural retina cells
[5]
. It is located almost exclusively in the neural cells of the retina
[5, 6]
, and it is synthesised in photoreceptor cells before incorporation into the extracellular matrix
[2]
. The role of purpurin as a trophic factor, mediating both cell adhesion and survival, seems clear but it may also have a subsidiary role as a minor retinol transporter in the retina based on its retinol binding capacity
[2]
. pRBP is also able to stimulate the adhesion of neural retina cells, although the serum protein is less active than purpurin
[6]
.

Structural notes: This subgroup shares a common β-barrel fold with the parent group. See
PIRSF036893
for a detailed description.

References

1.Retinol-binding protein: the transport protein for vitamin A in human plasma. Kanai M, Raz A, Goodman DS. J. Clin. Invest. 47, 2025-44, (1968). View articlePMID: 5675424

2.Sequence analysis, cellular localization, and expression of a neuroretina adhesion and cell survival molecule. Berman P, Gray P, Chen E, Keyser K, Ehrlich D, Karten H, LaCorbiere M, Esch F, Schubert D. Cell 51, 135-42, (1987). View articlePMID: 3652208

3.Vitamin A and retinoids in health and disease. Goodman DS. N. Engl. J. Med. 310, 1023-31, (1984). View articlePMID: 6369133

4.Ligand-dependent regulation of intracellular protein transport: effect of vitamin a on the secretion of the retinol-binding protein. Ronne H, Ocklind C, Wiman K, Rask L, Obrink B, Peterson PA. J. Cell Biol. 96, 907-10, (1983). View articlePMID: 6682115

5.Isolation of an adhesion-mediating protein from chick neural retina adherons. Schubert D, LaCorbiere M. J. Cell Biol. 101, 1071-7, (1985). View articlePMID: 2993313

6.A chick neural retina adhesion and survival molecule is a retinol-binding protein. Schubert D, LaCorbiere M, Esch F. J. Cell Biol. 102, 2295-301, (1986). View articlePMID: 3754874

7.The piscine plasma retinol-binding protein. Purification, partial amino acid sequence and interaction with mammalian transthyretin of rainbow trout (Oncorhynchus mykiss) retinol-binding protein. Berni R, Stoppini M, Zapponi MC. Eur. J. Biochem. 204, 99-106, (1992). View articlePMID: 1740159

8.Unique biochemical nature of carp retinol-binding protein. N-linked glycosylation and uncleavable NH2-terminal signal peptide. Bellovino D, Morimoto T, Mengheri E, Perozzi G, Garaguso I, Nobili F, Gaetani S. J. Biol. Chem. 276, 13949-56, (2001). View articlePMID: 11278316

9.Studies on the interaction between prealbumin, retinol-binding protein, and vitamin A. Peterson PA. J. Biol. Chem. 246, 44-9, (1971). PMID: 5541771

10.Cross talk between signaling and vitamin A transport by the retinol-binding protein receptor STRA6. Berry DC, O'Byrne SM, Vreeland AC, Blaner WS, Noy N. Mol. Cell. Biol. 32, 3164-75, (2012). View articlePMID: 22665496

GO terms

biological process

  • None

cellular component

  • None
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