scholarly journals The influence of soluble binding proteins on lipophile transport and metabolism in hepatocytes

1981 ◽  
Vol 195 (2) ◽  
pp. 441-452 ◽  
Author(s):  
E Tipping ◽  
B Ketterer
Keyword(s):  
Small Molecules ◽  
Intracellular Transport ◽  
Binding Proteins ◽  
Binding Protein ◽  
Protein A ◽  
Model Systems ◽  
Fatty Acid Binding ◽  
Order Of Magnitude ◽  
Intracellular Binding ◽  
Z Protein

A theory is presented that deals with the involvement of the intracellular binding proteins ligandin and aminoazodye-binding protein A (otherwise known as Z-protein or fatty-acid-binding protein) on the uptake and intracellular transport and metabolism of their ligands. Equations are derived that combine steady-state diffusional fluxes of small molecules that are (a) free in the aqueous phase of the cell, (b) bound to the two proteins and (c) partitioned into intracellular membranes, for model systems that resemble conditions in the rat hepatocyte. These equations are then combined with expressions for the enzyme-catalysed metabolic reactions undergone by these small molecules to assess the influence of diffusion rats on the overall metabolic rates. It is concluded that ligandin and protein A can enhance the rate of intracellular of their ligands by an order of magnitude or more and that this could make the hepatocyte several times more efficient in metabolizing these ligands. Various ways of testing this theory are discussed.

scholarly journals Interactions of small molecules with phospholipid bilayers. Binding to egg phosphatidylcholine of some organic anions (bromosulphophthalein, oestrone sulphate, haem and bilirubin) that bind to ligandin and aminoazo-dye-binding protein A

1979 ◽  
Vol 180 (2) ◽  
pp. 327-337 ◽  
Author(s):  
E Tipping ◽  
B Ketterer ◽  
L Christodoulides
Keyword(s):  
Intracellular Transport ◽  
Binding Protein ◽  
Equilibrium Dialysis ◽  
Protein A ◽  
Molar Ratio ◽  
Oestrone Sulphate ◽  
Dye Binding ◽  
Order Of Magnitude ◽  
Saturation Effects ◽  
Limiting Values

1. To assess the possible involvement of ligandin and aminoazo-dye-binding protein A in intracellular transport it is necessary to know how their ligands, most of which are molecules with hydrophobic moieties, interact with cellular membranes. To obtain such information we examined the interactions of bromosulphophthalein, oestrone sulphate, haem and bilirubin with aqueous dispersions of egg phosphatidylcholine and egg phosphatidylchone/cholesterol (1:1, molar ratio) by equilibrium dialysis and spectrophotometry. 2. In all four cases, saturation effects were observed. Values of Vmax (v = mol of compound bound/mol of lipid phosphorus) at 25 degrees C were: for bromosulphophthalein, approximately 0.1; for oestrone sulphate, approximately 0.25; for haem, approximately 0.25 (all at pH 7.4); and for bilirubin 0.1–0.2 (at pH 8.2). 3. Limiting values of v/c (c = unbound concentration) as v leads to 0 at 25 degrees C and pH 7.4 are: for bromosulphophthalein, 6.25 × 10(4) litre-mol-1; for oestrone sulphate, 7.8 × 10(2) litre-mol-1; for haem, 4.5 × 10(5) litre-mol-1; and for bilirubin, approximately 1.2 × 10(4) litre-mol-1. For haem the result depends on the assumption that only the monomeric form binds to the lipid. 4. The binding of each compound was decreased by cholesterol; bromosulphophthalein and oestrone sulphate were affected more than haem and bilirubin. 5. Bromosulphophthalein at saturating concentration decreased the limiting values of v/c of the other three compounds by approximately one order of magnitude. 6. By assuming that the interactions with egg phosphatidylcholine resemble those with the phospholipid components of mammalian intracellular membranes the binding data for phosphyatidylcholine, together with data for binding to the intracellular proteins ligandin and aminoazo-dye-binding protein A, enable the subcellular distributions of the four compounds to be estimated. For the rat hepatocyte up to 92, 51, 98 and 47% of the total bromosulphophthalein, oestrone sulphate, haem and bilirubin respectively may be membrane-bound.

scholarly journals Affinity purification of cellular retinoic acid-binding protein on 14-carboxy-13-cis-retinamide-sepharose 4B

1989 ◽  
Vol 262 (3) ◽  
pp. 917-922 ◽  
Author(s):  
R K Singh ◽  
B P Sani ◽  
M I Dawson ◽  
Y F Shealy
Keyword(s):  
Retinoic Acid ◽  
Carboxy Group ◽  
Binding Proteins ◽  
Binding Protein ◽  
Polyacrylamide Gel Electrophoresis ◽  
Biologically Active ◽  
Amide Bond ◽  
Gel Chromatography ◽  
Fatty Acid Binding ◽  
Sepharose 4B

A biologically active bifunctional retinoid, ethyl 14-carboxyretinoate, has been synthesized and shown to bind cellular retinoic acid (RA)-binding protein (CRABP) via its free carboxy group. We describe herein the synthesis of 14-carboxy-13-cis-retinamide-Sepharose 4B, which is an affinity matrix bearing an all-trans-RA moiety, and thus was used to purify and characterize CRABP from chick-embryo skin. An amide bond was first formed between the free carboxy group of the retinoid and a primary amino group of aminohexyl-Sepharose 4B, by reaction with carbodi-imide, and the ester group of the resin-bound retinoid was then hydrolysed in an alkaline medium. Polyacrylamide-gel electrophoresis and f.p.l.c. Superose column-chromatographic analysis demonstrated that the affinity-purified CRABP (Mr 15,000) was close to electrophoretic homogeneity (greater than 90%) and specifically interacts with RA. By using affinity gel chromatography, conversion of holo-CRABP into apo-CRABP by treatment with p-hydroxymercuribenzoate and a possible involvement of a thiol group in RA binding to CRABP were established. This affinity procedure provides several advantages: (i) 14-carboxy-13-cis-retinamide-Sepharose exhibited high efficiency and selectivity for RA-binding protein (i.e. retinol- or fatty-acid-binding proteins did not bind); (ii) the presence of the amide linkage between the ligand and the matrix makes this affinity resin relatively stable to cytosolic enzymes; and (iii) other RA-binding proteins, e.g. nuclear receptor(s), may be purified.

LIGANDIN AND PROTEIN A: INTRACELLULAR BINDING PROTEINS

1978 ◽  
pp. 79-94 ◽  
Author(s):  
B. Ketterer ◽  
T. Carne ◽  
E. Tipping
Keyword(s):  
Binding Proteins ◽  
Protein A ◽  
Intracellular Binding

Inhibition of binding to fatty acid binding protein reduces the intracellular transport of fatty acids

1996 ◽  
Vol 271 (1) ◽  
pp. G113-G120 ◽  
Author(s):  
B. A. Luxon
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Intracellular Transport ◽  
Fatty Acid Binding Protein ◽  
Binding Protein ◽  
Female Rats ◽  
Dependent Manner ◽  
Fatty Acid Binding ◽  
Acid Binding Protein ◽  
Cytoplasmic Transport

Male livers, containing lesser amounts of fatty acid binding protein (FABP), utilize fatty acids more slowly than female livers. Conventional wisdom dictates that FABP stimulates fatty acid use by increasing cytoplasmic transport rates. Previously, we showed that the cytoplasmic diffusion of a fatty acid analogue [12-N-methyl-7-nitrobenzo-2-oxa-1,3-diazol-amino stearate (NBD-stearate)] is faster in female hepatocytes, paralleling the larger amounts of FABP. Sex differences in other cytoplasmic factors could also lead to faster diffusion, independent of FABP levels. The aim of this study was to determine the effect of inhibition of fatty acid binding to FABP on the directly measured intracellular transport rate of NBD-stearate. The binding of NBD-stearate to FABP was reduced by incubating hepatocytes isolated from male and female rats with alpha-bromo-palmitate (0-1,500 microM), a modified long-chain fatty acid that binds to FABP. The inhibition by alpha-bromo-palmitate on NBD-stearate binding to FABP was measured with the use of centrifugation to separate cytosol from cytoplasmic membranes. Laser photobleaching (fluorescence recovery after photobleaching) was used to measure the cytoplasmic diffusion of NBD-stearate in hepatocytes. Alpha-Bromo-palmitate incubation reduced NBD-stearate binding to FABP in a dose-dependent manner. The measured diffusion rate was also reduced in proportion to the degree of binding inhibition. We conclude that cytoplasmic transport of NBD-stearate is modulated by binding to soluble proteins like FABP. FABP enhances diffusive transport by reducing binding to immobile cytosolic membranes.

Adipocyte fatty acid-binding protein: A predictive marker of metabolic syndrome

2017 ◽  
Vol 263 ◽  
pp. e202
Author(s):  
Michal Karpisek ◽  
David Stejskal ◽  
Martina Hlozankova ◽  
Viktor Ruzicka
Keyword(s):  
Metabolic Syndrome ◽  
Fatty Acid ◽  
Fatty Acid Binding Protein ◽  
Binding Protein ◽  
Protein A ◽  
Predictive Marker ◽  
Fatty Acid Binding ◽  
Acid Binding Protein
Sign in / Sign up

Export Citation Format

Share Document