scholarly journals Tissue distribution of the receptor for plasma retinol-binding protein

1995 ◽  
Vol 305 (2) ◽  
pp. 419-424 ◽  
Author(s):  
S Smeland ◽  
T Bjerknes ◽  
L Malaba ◽  
W Eskild ◽  
K R Norum ◽  
...  
Keyword(s):  
Tissue Distribution ◽  
Specific Binding ◽  
Binding Protein ◽  
Cell Types ◽  
Binding Activity ◽  
Retinol Binding Protein ◽  
Scatchard Analysis ◽  
High Binding ◽  
Differentiated Cells ◽  
Protein Receptor

The tissue distribution of the retinol-binding-protein receptor has been studied by using a cell-free binding assay. High binding activity was found in placenta, retina pigment epithelial cells, bone marrow and kidneys. Specific binding activity was also found in the small intestines, spleen and liver, and to a lesser extent in lung. Scatchard analysis revealed that the difference in binding activity was due to variations in receptor level and not affinity changes. When the kidneys were separated into cortex and medulla we found that almost all the specific binding activity present in kidneys was recovered in the cortex. The choroid plexus, an important site in the delivery of nutrients to the cerebrospinal fluid, expressed very high binding activity. The pineal gland, which has been shown to store vitamin A, also showed high binding activity. Testes from immature animals showed higher binding activity than testes from mature rabbits. Cultured undifferentiated kidney keratinocytes showed about 40 times higher binding activity than differentiated cells. Skin fibroblasts demonstrated no binding activity. In conclusion, the data presented in this report show that the level of the retinol-binding-protein receptor varies considerably between cell types. The observed tissue distribution of the receptor agrees well with the present knowledge on retinol function and metabolism by various cells.

scholarly journals Solubilization and purification of the retinol-binding protein receptor from human placental membranes

1994 ◽  
Vol 302 (1) ◽  
pp. 245-251 ◽  
Author(s):  
A Sivaprasadarao ◽  
M Boudjelal ◽  
J B C Findlay
Keyword(s):  
Binding Protein ◽  
Binding Activity ◽  
Retinol Binding Protein ◽  
Protein Receptor ◽  
Sds Page ◽  
Minor Protein ◽  
Membrane Bound ◽  
Placental Membranes ◽  
Poly Ethylene ◽  
Solubilized Form

The membrane receptor for retinol-binding protein (RBP) has been solubilized from human placental brush-border membranes with octyl-beta-glucoside, Nonidet P-40 and CHAPS. A method, based on the preferential precipitation of 125I-RBP-receptor complex with poly(ethylene glycol) 8000, was developed in order to measure the RBP-binding activity in the detergent extracts. The receptor was fairly stable (4 degrees C, 7 days) in octyl-beta-glucoside and Nonidet P-40, but quickly lost activity in CHAPS. The detergent-solubilized form retained all the properties characteristic of the membrane-bound protein, except for a small decrease in affinity for RBP (3- and 7-fold in Nonidet P-40 and octyl-beta-glucoside respectively). The receptor was isolated using recombinant RBP coupled to Reacti-Gel 6X affinity matrix. The purified material contained major and minor protein species of 63 and 55 kDa respectively on SDS/PAGE.

Onchocerca retinol- and ivermectin-binding protein activity

Parasitology ◽  
1996 ◽  
Vol 112 (2) ◽  
pp. 221-225 ◽  
Author(s):  
P. G. Lal ◽  
E. R. James
Keyword(s):  
Adult Worm ◽  
Specific Binding ◽  
Binding Protein ◽  
Binding Activity ◽  
Retinol Binding Protein ◽  
Size Exclusion ◽  
Protein Activity ◽  
Molecular Weights ◽  
Molar Excess ◽  
Exclusion Chromatography

SummaryThe presence of retinol-binding protein (RBP) activity in Onchocerca cervicalis adult worms and interaction with ivermectin has been studied using high pressure size exclusion chromatography (HPSEC). Four distinct peaks of [3H]-retinol incorporation were obtained corresponding to approximate molecular weights of 150, 67, 19·7 and 4–6 kDa, the 2 smaller Mr peaks accounting for most of the binding activity. Competition for binding using non-labelled retinol at 200-fold molar excess indicated that specific binding of retinol occurred only to the 19–7 kDa fraction. Competition by ivermectin also inhibited binding of [3H]-retinol to the third peak. Following incubation with [3H]-ivermectin & peaks of similar molecular weights were also detected by HPSEC in soluble adult worm homogenate, However, in this case the 150 kDa fraction was most prominent. Both non-labelled ivermectin and non-labelled retinol at 200-fold molar excess reduced binding of [3H]-ivermectin to all & fractions. These data indicate that the putative Onchocerca RBP has an approximate molecular weight of 19·7 kDa, that retinol also binds to 3 additional fractions non-specifically, that the pattern of binding of ivermectin to adult worm material is quantitatively and qualitatively different from the binding exhibited by retinol, and that ivermectin interferes with the binding of retinol to the 19·7 kDa Onchocerca protein.

scholarly journals Structure-function studies on human retinol-binding protein using site-directed mutagenesis

1994 ◽  
Vol 300 (2) ◽  
pp. 437-442 ◽  
Author(s):  
A Sivaprasadarao ◽  
J B Findlay
Keyword(s):  
Cell Surface ◽  
Specific Binding ◽  
Binding Protein ◽  
Specific Interaction ◽  
Binding Activity ◽  
Site Directed Mutagenesis ◽  
Retinol Binding Protein ◽  
Cell Surface Receptor ◽  
Directed Mutagenesis ◽  
Surface Receptor

Retinol-binding protein (RBP) transports vitamin A in the plasma. It consists of eight anti-parallel beta-strands (A to H) that fold to form an orthogonal barrel. The loops connecting the strands A and B, C and D, and E and F form the entrance to the binding site in the barrel. The retinol molecule is found deep inside this barrel. Apart from its specific interaction with retinol, RBP is involved in two other molecular-recognition properties, that is it binds to transthyretin (TTR), another serum protein, and to a cell-surface receptor. Using site-directed mutagenesis, specific changes were made to the loop regions of human RBP and the resultant mutant proteins were tested for their ability to bind to retinol, to TTR and to the RBP receptor. While all the variants retained their ability to bind retinol, that in which residues 92 to 98 of the loop E-F were deleted completely lost its ability to interact with TTR, but retained some binding activity for the receptor. In contrast, the double mutant in which leucine residues at positions 63 and 64 of the loop C-D were changed to arginine and serine respectively partially retained its TTR-binding ability, but completely lost its affinity for the RBP receptor. Mutation of Leu-35 of loop A-B to valine revealed no apparent effect on any of the binding activities of RBP. However, substitution of leucine for proline at position 35 markedly reduced the affinity of the protein for TTR, but showed no apparent change in its receptor-binding activity. These results demonstrate that RBP interacts with both TTR and the receptor via loops C-D and E-F. The binding sites, however, are overlapping rather than identical. RBP also appears to make an additional contact with TTR via its loop A-B. A further implication of these results is that RBP, when bound to TTR, cannot bind simultaneously to the receptor. This observation is consistent with our previously proposed mechanism for delivery of retinol to target tissues [Sivaprasadarao and Findlay (1988) Biochem. J. 255, 571-579], according to which retinol delivery involves specific binding of RBP to the cell-surface receptor, an interaction that triggers release of retinol from RBP to the bound cell rather than internalization of retinol-RBP complex.

scholarly journals Membrane receptor for odour-binding proteins

1996 ◽  
Vol 317 (1) ◽  
pp. 23-27 ◽  
Author(s):  
Mohamed BOUDJELAL ◽  
Asipu SIVAPRASADARAO ◽  
John B. C FINDLAY
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Binding Protein ◽  
Structural Similarity ◽  
Thiol Group ◽  
The Body ◽  
Retinol Binding Protein ◽  
Proteinase K ◽  
Scatchard Analysis ◽  
Major Urinary Proteins

Specific binding of 125I-labelled bovine odour-binding protein (OBP) to isolated membranes from nasal mucosa was demonstrated. The interaction reached equilibrium within 30 min at 37 °C and was reversible. A Scatchard analysis of the equilibrium binding revealed a single population of binding sites, with the calculated equilibrium dissociation constant and maximum number of binding sites being 2.25±0.5 μM and 18.5±2 pmol/mg of membrane protein respectively (n = 2). Receptor activity was decreased on digestion by trypsin, proteinase K or endoglycosidase H, was heat labile and was sensitive to thiol-group-specific reagents. With the exception of rat and mouse major urinary proteins, which exhibit a high degree of structural similarity with OBP and bind similar ligands, other members of the lipocalin family, such as retinol-binding protein and β-lactoglobulin, failed to inhibit the binding of 125I-labelled OBP to its receptor. The receptor seems not to be restricted to olfactory tissues, as it was detected in a variety of other tissues. This suggests that OBP is unlikely to play a role only in olfactory signal transduction. It might have a much broader role within the body; possibilities include a role in detoxification or signalling.

scholarly journals Transcriptional and Posttranscriptional Regulation of Insulin-Like Growth Factor Binding Protein-3 by Cyclic Adenosine 3′,5′-Monophosphate: Messenger RNA Stabilization Is Accompanied by Decreased Binding of a 42-kDa Protein to a Uridine-Rich Domain in the 3′-Untranslated Region

1999 ◽  
Vol 13 (3) ◽  
pp. 495-504
Author(s):  
N. E. Erondu ◽  
J. Nwankwo ◽  
Y. Zhong ◽  
M. Boes ◽  
B. Dake ◽  
...  
Keyword(s):  
Growth Factor ◽  
Untranslated Region ◽  
Specific Binding ◽  
Binding Protein ◽  
Binding Activity ◽  
Insulin Like Growth Factor ◽  
Factor Binding ◽  
Mdbk Cells ◽  
Camp Induction ◽  
Igfbp 3

Abstract The Madin Darby bovine kidney (MDBK) cell line was used to investigate the mechanisms underlying the cAMP regulation of insulin-like growth factor binding protein-3 (IGFBP-3) gene expression. Treatment of confluent monolayers either with forskolin or cAMP produced a 60- to 75-fold induction of IGFBP-3 mRNA and protein levels. This effect did not require new protein synthesis as inhibition of translation by cycloheximide actually caused a 2-fold increase in the cAMP induction. The rates of IGFBP-3 gene transcription, assessed by nuclear run-on assays, increased approximately 15-fold in cells exposed to cAMP. In addition, the half-life of the IGFBP-3 mRNA transcript was increased ∼3-fold in the presence of cAMP. Gel mobility shift and competition experiments revealed the specific binding of an approximately 42-kDa cytoplasmic protein factor to the 3′-untranslated region (3′-UTR) of the IGFBP-3 mRNA. A 21-nucleotide uridine-rich segment that contained no AUUUA motif was sufficient for the specific binding. The binding activity of this protein was reduced after cAMP treatment but was increased by phosphatase treatment. In conclusion, the cAMP induction of IGFBP-3 mRNA in MDBK cells occurred at both the transcriptional and posttranscriptional levels. The IGFBP-3 mRNA stabilization in MDBK cells probably involved the phosphorylation of a member of the family of U-rich region mRNA-binding proteins and is the first reported member whose RNA-binding activity is reduced by cAMP.

scholarly journals Structural Studies of Retinol-Binding Protein Receptor RBPR2

2018 ◽  
Vol 114 (3) ◽  
pp. 424a
Author(s):  
Jonathan Kim ◽  
Yong Zi Tan ◽  
Brianna Costabile ◽  
Yunting Chen ◽  
Filippo Mancia
Keyword(s):  
Binding Protein ◽  
Retinol Binding Protein ◽  
Structural Studies ◽  
Protein Receptor
Sign in / Sign up

Export Citation Format

Share Document