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Hugo L. Monaco - One of the best experts on this subject based on the ideXlab platform.

  • the transthyretin Retinol Binding Protein complex
    Biochimica et Biophysica Acta, 2000
    Co-Authors: Hugo L. Monaco
    Abstract:

    Retinol-Binding Protein (RBP), the specific transporter in plasma of Retinol and transthyretin (TTR), transporter of thyroid hormones, form in higher vertebrates under physiological conditions, a macromolecular complex that prevents glomerular filtration of the low molecular mass RBP. The crystal structures of two RBP–TTR complexes have shed light on many aspects of the interaction between the two transporters and explained observations made with other experimental methods. Since higher levels of RBP are associated with insulin resistance in obesity and type 2 diabetes it has been suggested that dissociation of the complex with the consequent renal elimination of RBP might be a way to treat the disease.

  • Structure of a complex of two plasma Proteins: transthyretin and Retinol-Binding Protein.
    Science (New York N.Y.), 1995
    Co-Authors: Hugo L. Monaco, Menico Rizzi, Alessandro Coda
    Abstract:

    The three-dimensional structure of the complex formed by two plasma Proteins, transthyretin and Retinol-Binding Protein, was determined from x-ray diffraction data to a nominal resolution of 3.1 angstroms. One tetramer of transthyretin was bound to two molecules of Retinol-Binding Protein. The two Retinol-Binding Protein molecules established molecular interactions with the same transthyretin dimer, and each also made contacts with one of the other two monomers. Thus, the other two potential Binding sites in a transthyretin tetramer were blocked. The amino acid residues of the Retinol-Binding Protein that were involved in the contacts were close to the Retinol-Binding site.

  • Crystallization of the macromolecular complex transthyretin-Retinol-Binding Protein.
    Journal of molecular biology, 1994
    Co-Authors: Hugo L. Monaco, Menico Rizzi, Filippo Mancia, Allessandro Coda
    Abstract:

    Single crystals of the macromolecular complex transthyretin-Retinol-Binding Protein have been obtained. Transthyretin is a carrier of the hormone thyroxine in plasma whereas Retinol-Binding Protein is the specific transporter of the alcohol form of vitamin A in the same medium. This macromolecular complex is found under physiological conditions in plasma and is believed to play an important physiological role. The complex can be formed in vitro by Proteins purified from different species. Our crystals are grown with chicken Retinol-Binding Protein complexed to human transthyretin. They are grown by equilibrium dialysis versus 2.3 M ammonium sulphate, 3% ethylene glycol buffered with 0.1 M succinate (pH 5.5). Their space group is I222 (or I2(1)2(1)2(1)) with unit cell parameters a = 222.4 A, b = 163.4 A and c = 55.5 A. Using a conventional X-ray source, we have collected a complete data set of the crystals to a nominal resolution of 3.1 A.

William S. Blaner - One of the best experts on this subject based on the ideXlab platform.

  • Retinol-Binding Protein 2 (RBP2): biology and pathobiology.
    Critical reviews in biochemistry and molecular biology, 2020
    Co-Authors: William S. Blaner, Pierre-jacques Brun, Rossana M. Calderon, Marcin Golczak
    Abstract:

    Retinol-Binding Protein 2 (RBP2; originally cellular Retinol-Binding Protein, type II (CRBPII)) is a 16 kDa cytosolic Protein that in the adult is localized predominantly to absorptive cells of the...

  • Interactions of Retinol with Binding Proteins: studies with rat cellular Retinol-Binding Protein and with rat Retinol-Binding Protein.
    Biochemistry, 1991
    Co-Authors: Noa Noy, William S. Blaner
    Abstract:

    The interactions of Retinol with rat cellular Retinol-Binding Protein (CRBP) and with rat serum Retinol-Binding Protein (RBP) were studied. The equilibrium dissociation constants of the two Retinol-Protein complexes (Kd) were found to be 13 x 10(-9) and 20 x 10(-9) M for CRBP and for RBP, respectively. The kinetic parameters governing the interactions of Retinol with the two Binding Proteins were also studied. It was found that although the equilibrium dissociation constants of the two Retinol-Protein complexes were similar, Retinol interacted with CRBP 3-5-fold faster than with RBP; the rate constants for dissociation of Retinol from CRBP and from RBP (koff) were 0.57 and 0.18 min-1, respectively. The rate constants for association of Retinol with the two Proteins (kon) were calculated from the expression: Kd = koff/kon. The kon's for Retinol associating with CRBP and with RBP were found to be 4.4 x 10(7) and 0.9 x 10(7) M-1 min-1, respectively. The data suggest that the initial events of uptake of Retinol by cells are not rate-limiting for this process and that the rate of uptake is probably determined by the rate of metabolism of this ligand. The data indicate further that the distribution of Retinol between RBP in blood and CRBP in cytosol is at equilibrium and that intracellular levels of Retinol are regulated by the levels of CRBP.

Guntram Schernthaner - One of the best experts on this subject based on the ideXlab platform.

Rune Blomhoff - One of the best experts on this subject based on the ideXlab platform.

  • retinyl ester storage is altered in liver stellate cells and in hl60 cells transfected with cellular Retinol Binding Protein type i
    The International Journal of Biochemistry & Cell Biology, 1997
    Co-Authors: Astrid Nilsson, Kaare R. Norum, Gunhild Troen, Lizette B Petersen, Sjur Reppe, Rune Blomhoff
    Abstract:

    Abstract It is suggested that cellular Retinol-Binding Proteins are important for intracellular metabolism of Retinol. Retinol bound to cellular Retinol-Binding Proteins may be esterified with long chain fatty acids by the enzyme lecithin: Retinol acyltransferase or may be oxidized to retinoic acid metabolites used in the mechanism of action of vitamin A. The aim of this present report was to determine whether altered levels of cellular Retinol-Binding Protein type I influenced Retinol storage and activation. Two different cell types have been examined after transfection with vectors producing sense or antisense mRNA for cellular Retinol-Binding Protein type 1. When HL60 cells were transfected with the expression vector for sense cellular Retinol-Binding Protein type I high amounts of cellular Retinol-Binding Protein type I mRNA and Protein were produced. We observed that HL60 cells esterified less Retinol than control cells without cellular Retinol-Binding Protein type I. Cellular Retinol-Binding Protein type I had, however, no effects on the proliferation or differentiation of HL60 cells by retinoids. Liver stellate cells transfected with the vector for sense cellular Retinol-Binding Protein type I esterified more Retinol than cells transfected with the expression vector for antisense cellular Retinol-Binding Protein type I, while Retinol esterification in control cells was intermediate. In conclusion, our data show that cellular Retinol-Binding Protein type I influences Retinol esterification both in liver stellate cells and in HL60 cells.

  • The C-terminal RNLL sequence of the plasma Retinol-Binding Protein is not responsible for its intracellular retention.
    Biochemical and biophysical research communications, 1996
    Co-Authors: Vasanti Natarajan, Rune Blomhoff, Sjur Reppe, Kirsten B. Holven, Jan Øivind Moskaug
    Abstract:

    Abstract An in vitro model system using COS cells that transiently express human plasma Retinol Binding Protein has been set up in which we are able to mimic the Retinol dependent secretion of this Protein observed in hepatocytes. In the absence of its ligand, plasma Retinol Binding Protein is retained in the endoplasmic reticulum. It contains a C-terminal sequence, RNLL, that could function as a cryptic KDEL motif and thus be responsible for its retention in the endoplasmic reticulum. The model system has been used to test a mutant lacking these four last amino acids for retention and Retinol induced secretion. The results obtained show that although plasma Retinol Binding Protein is retained in the endoplasmic reticulum, the RNLL sequence does not seem to be responsible for its retention.

  • Retinol Binding Protein and asialo orosomucoid are taken up by different pathways in liver cells
    Journal of Biological Chemistry, 1995
    Co-Authors: L Malaba, Sigbjorn Smeland, Trond Berg, Kaare R. Norum, Haruki Senoo, Rune Blomhoff, G M Kindberg
    Abstract:

    Abstract The intracellular transport and degradation of in vivo endocytosed Retinol-Binding Protein was compared with that of asialo-orosomucoid, a marker for receptor-mediated endocytosis through coated pits. The transport pathways were studied in rat liver cells by means of subcellular fractionation in Nycodenz and sucrose density gradients and by immunoelectron microscopy. Retinol-Binding Protein and asialo-orosomucoid were labeled by covalent attachment of radioiodinated tyramine cellobiose, an adduct which is incapable of crossing cellular membranes and thus provides a marker for the organelles where the Protein has been taken up and degraded. The data obtained from subcellular fractionation studies, as well as from immunoelectron microscopy, showed that Retinol-Binding Protein and asialo-orosomucoid were initially localized in different endocytic vesicles. Retinol-Binding Protein co-localized in density gradients with markers for potocytosis, an alternative endocytic pathway which uses internalization through caveolae instead of clathrin-coated pits. Later, Retinol-Binding Protein and asialo-orosomucoid comigrated in the gradients and they were also observed in the same larger vesicles by immunoelectron microscopy. These data suggest that Retinol-Binding Protein is taken up by liver cells by potocytosis and that a fraction of the Retinol-Binding Protein is later transferred to larger vesicles located deeper in the cytoplasm where degradation takes place.

Sharon T. Franklin - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Supplemental, Dietary Vitamin A on Retinol-Binding Protein Concentrations in the Plasma of Preruminant Calves,
    Journal of dairy science, 2001
    Co-Authors: Brian J. Nonnecke, M.p. Roberts, James D. Godkin, Ronald L. Horst, D.c. Hammell, Sharon T. Franklin
    Abstract:

    Abstract Transport of Retinol (vitamin A alcohol) from retinoid stores in the liver to target tissues is accomplished exclusively by a specific plasma Protein, Retinol-Binding Protein. Within individuals, Retinol-Binding Protein concentrations in plasma are regulated and remain constant except in extremes of vitamin A nutriture or in disease. In the present study, Retinol-Binding Protein concentrations in plasma from preruminant calves supplemented with 0, 1700 (i.e., current NRC requirement), 34,000, or 68,000 IU of vitamin A daily from birth to 27 d of age (n = 6/treatment) were quantified. Retinol-Binding Protein concentrations at birth averaged 21 μ g/ml (n = 24) or approximately 50% of concentrations in dairy heifers and cows. Plasma Retinol and Retinol-Binding Protein concentrations were correlated positively, corroborating the role of vitamin A nutriture in the regulation of Retinol-Binding Protein secretion from the liver. In this regard, dietary vitamin A influenced positively Retinol and Retinol-Binding Protein concentrations and, as a consequence, the degree of saturation of Retinol-Binding Protein with Retinol. At 27 d of age, calves fed ≥34,000 IU of vitamin A had substantially higher Retinol and Retinol-Binding Protein concentrations than did calves fed ≤1700 IU of vitamin A, indicating that dietary vitamin A effects positively vitamin A status. The data also suggest that the current NRC requirement may not be sufficient to assure vitamin A adequacy in preruminant calves. Percent saturation of Retinol-Binding Protein with Retinol in all calves was