InterPro : IPR002449

Name  Retinol binding protein/Purpurin Short Name  Retinol-bd/Purpurin
Type  Family Description  Proteins in this family include plasma retinol binding protein (pRBP) and purpurin. They are implicated in the biological action of retinoids, principally retinol (vitamin A), retinal, and retinyl palmitate, as well as their numerous synthetic analogues.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 []. In mammals, pRBP binds to transthyretin in the plasma, preventing the loss of pRBP through glomerular filtration []. 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 []. 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 [].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 [].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 []. It is located almost exclusively in the neural cells of the retina [, ], and it is synthesised in photoreceptor cells before incorporation into the extracellular matrix []. 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 []. pRBP is also able to stimulate the adhesion of neural retina cells, although the serum protein is less active than purpurin [].Structural notes: This subgroup shares a common beta-barrel fold with the parent group. See for a detailed description.

Sequence Features

GO Displayer


InterPro protein domain ID --> Contigs



0 Child Features

1 Contains

Id Name Short Name Type
IPR022272 Lipocalin family conserved site Lipocalin_CS Conserved_site

0 Found In

1 Parent Features

Id Name Short Name Type
IPR022271 Lipocalin, ApoD type Lipocalin_ApoD Family

8 Publications

First Author Title Year Journal Volume Pages
Schubert D A chick neural retina adhesion and survival molecule is a retinol-binding protein. 1986 J Cell Biol 102 2295-301
Ronne H Ligand-dependent regulation of intracellular protein transport: effect of vitamin a on the secretion of the retinol-binding protein. 1983 J Cell Biol 96 907-10
Berni R The piscine plasma retinol-binding protein. Purification, partial amino acid sequence and interaction with mammalian transthyretin of rainbow trout (Oncorhynchus mykiss) retinol-binding protein. 1992 Eur J Biochem 204 99-106
Schubert D Isolation of an adhesion-mediating protein from chick neural retina adherons. 1985 J Cell Biol 101 1071-7
Bellovino D Unique biochemical nature of carp retinol-binding protein. N-linked glycosylation and uncleavable NH2-terminal signal peptide. 2001 J Biol Chem 276 13949-56
Goodman DS Vitamin A and retinoids in health and disease. 1984 N Engl J Med 310 1023-31
Berman P Sequence analysis, cellular localization, and expression of a neuroretina adhesion and cell survival molecule. 1987 Cell 51 135-42
Kanai M Retinol-binding protein: the transport protein for vitamin A in human plasma. 1968 J Clin Invest 47 2025-44

To cite PlanMine, please refer to the following publication:

Rozanski, A., Moon, H., Brandl, H., Martín-Durán, J. M., Grohme, M., Hüttner, K., Bartscherer, K., Henry, I., & Rink, J. C.
PlanMine 3.0—improvements to a mineable resource of flatworm biology and biodiversity
Nucleic Acids Research, gky1070. doi:10.1093/nar/gky1070 (2018)