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Biomedical subjects

F Palmieri

Publications and source records attributed to F Palmieri.

At least 145 records · Page 8Linked to original sources
PubMed1989

Inhibition of the mitochondrial phosphate carrier by a reaction with a carboxyl group reagent.

The effect of N-ethyl-5-phenylisoxazolium 3"-sulfonate (Woodward's reagent K, WRK), a reagent forming covalent bonds with protein carboxyl groups, on the activity of the mitochondrial phosphate carrier was investigated. Treatment with WRK of mitochondria or of extracted carrier incorporated into liposomes, inhibited phosphate transport in a reconstituted liposomal system. Increasing the binding of WRK resulted in increased inhibition: the modified carrier protein showed a reduced affinity for phosphate, but binding of WRK had no effect on the Vmax of phosphate transport. It was concluded that WRK caused a conformational change in the carrier protein not involving the phosphate or H+ carrier sites such that its affinity for phosphate was lowered.

Animals↗
PubMed1989

Purification and properties of the voltage-dependent anion channel of the outer mitochondrial membrane.

The methods for the purification of functionally active mitochondrial porin or voltage-dependent anion channel of the outer mitochondrial membrane are critically evaluated. Two rapid and efficient methods are now available. Both make use of a hydroxyapatite/celite column as a single chromatographic step. However, in one method with long polar head-group detergents, porin passes through the column, whereas in the other method, with shorter polar head-group detergents, porin is first bound to the column and then eluted by the addition of salts. On the basis of these results, a model for the arrangement of porin in the detergent-protein micelles is proposed.

Animals↗
PubMed1989

Demonstration and characterization of human cardiac porin: a voltage-dependent channel involved in adenine nucleotide movement across the outer mitochondrial membrane.

The porins are a class of voltage-dependent, anion-selective, channel-forming proteins located in the outer mitochondrial membrane (OMM). The porins are responsible for passage of adenine nucleotides across the OMM, as well as for specific binding of hexokinase and glycerol kinase. This porin-kinase complex has direct access to ATP generated by mitochondrial oxidative phosphorylation and may be important in the regulation of glycolysis. Porin had not been described previously in humans but, due to its importance in bioenergetics, would be expected to be present, especially in organs requiring a large and constant supply of energy. We therefore postulated that porin would occur in human myocardium where it would be important in cardiac function. Polyclonal antibodies to bovine myocardial and rat liver porins were utilized in transblotting experiments after polyacrylamide gel electrophoresis of human heart preparations from atria, ventricles, papillary muscles, and interventricular septum. These immunoblots demonstrated selective staining of a 34-kDa band. This was identical to the results obtained with purified porin and the antibodies. Also notable was the finding that the vast majority of this staining was found in the homogenate pellet after high speed centrifugation (20,000g), as would be expected for a mitochondrial protein. The demonstration of human cardiac porin by immunoblotting with rat liver and bovine myocardial porin antibodies is the first demonstration of cross-species identification of the porins. The success of this approach undoubtedly occurred because of strong homology between porins from a variety of species.

Adenine Nucleotides↗
PubMed1988

Interaction of phenylisothiocyanates with the mitochondrial phosphate carrier. I. Covalent modification and inhibition of phosphate transport.

The effects of phenylisothiocyanate (PITC) and of the polar analogue p-sulfophenylisothiocyanate (p-sulfoPITC) on the phosphate carrier of bovine heart mitochondria have been investigated. Incubation of mitochondria with the two phenylisothiocyanates leads to inhibition of the phosphate carrier protein. The inhibition of phosphate transport by PITC is unaffected by the addition of dithioerythritol (DTE) or by variation of the pH. The inhibition by p-sulfoPITC is in part removed by DTE; the remaining inactivation of the phosphate carrier, which can be attributed to the reaction with NH2 groups, is temperature and pH-dependent. Inhibition of phosphate transport by both p-sulfoPITC and PITC depends on the time of incubation and the concentration of the inhibitor. Preincubation with mersalyl protects the carrier protein against the inactivation by p-sulfoPITC but not against PITC. Other SH reagents tested do not show any protective effect. It can thus be concluded that two types of lysine residues are essential for the activity of the phosphate carrier. Lysine(s) of the former type are located at the surface of the membrane and are topologically related to the functional SH groups of the protein. Lysine residue(s) of the latter type are buried in the hydrophobic phase of the membrane.

Animals↗
PubMed1988

Inhibition and labelling of the mitochondrial 2-oxoglutarate carrier by eosin-5-maleimide.

Unlike hydrophobic maleimides, eosin-5-maleimide and to a lesser extent other relatively polar maleimides inhibit the 2-oxoglutarate carrier of bovine heart mitochondria. The impermeable eosin-5-maleimide labels the 2-oxoglutarate carrier in intact mitochondria but not in submitochondrial particles. 2-Oxoglutarate protects the carrier against inactivation by eosin-5-maleimide and decreases the fluorescence associated with the purified protein. Other anions which are not substrates of the carrier have no protective effect. It is concluded that sulfhydryl groups essential for the activity of the 2-oxoglutarate carrier are located at the cytosolic face of the inner mitochondrial membrane. They appear to be present at the substrate-binding site and located in a hydrophilic environment.

Biological Transport↗
PubMed1988

Purification and reconstitution of two anion carriers from rat liver mitochondria: the dicarboxylate and the 2-oxoglutarate carrier.

Two anion-transporting systems, i.e., the dicarboxylate carrier and the 2-oxoglutarate carrier, have been purified from rat liver mitochondria and functionally identified. The dicarboxylate carrier has been isolated in active form by hydroxyapatite chromatography after partial removal of the solubilizing detergent Triton X-114 from the mitochondrial extract. The SDS gel electrophoresis of this preparation consists mainly of one protein band with an apparent Mr of 28,000, identified as the dicarboxylate carrier. Complete purification of the 28 kDa protein in inactive form has been achieved by sequential chromatography on hydroxyapatite and Celite followed by SDS extraction of the retained protein. The 2-oxoglutarate carrier has been purified by hydroxyapatite chromatography after extensive removal of Triton X-114 from the detergent extract. SDS gel electrophoresis of the purified fraction shows a single band with an apparent Mr of 32,500. When reconstituted into liposomes, the functional properties of the two isolated carrier proteins resemble closely those of the dicarboxylate and the 2-oxoglutarate transport systems characterized in mitochondria.

Animals↗
PubMed1987

A simple and rapid method for the purification of the mitochondrial porin from mammalian tissues.

A new, simple and rapid procedure for the purification of high amounts of mitochondrial porins from different tissues of mammalia is described. The method consists in a single step hydroxyapatite/celite chromatography of Triton X-100 solubilized mitochondrial membranes. For optimal purification several factors are critical such as the absence of salts, a low protein/detergent ratio and an exact hydroxyapatite/celite ratio of 2:1.

Animals↗
PubMed1987

Reconstitution of the malate/aspartate shuttle from mitochondria.

The isolated aspartate/glutamate carrier and oxoglutarate carrier from mitochondria were coreconstituted into phospholipid vesicles. Reconstitution of the functionally active carrier proteins with high protein/lipid ratios was achieved by detergent removal on hydrophobic ion-exchange columns. A simplified version of the mitochondrial malate/aspartate shuttle was constructed by inclusion of glutamate-oxaloacetate transaminase and the substrates aspartate and oxaloacetate within the interior of the liposomes. Addition of external glutamate led to internal production of oxoglutarate which could be exchanged against externally added labeled malate. The reconstitution procedure was characterized with respect to the optimum ratio of reconstituted carrier proteins, the lipid concentration, and the concentration of internal substrates.

Amino Acid Transport Systems, Acidic↗
PubMed1987

Porin pores of mitochondrial outer membranes from high and low eukaryotic cells: biochemical and biophysical characterization.

The mitochondrial porins from mammalian tissues and from low eukaryotic cells were purified with a high yield, and their biochemical and functional properties were investigated. When analyzed by SDS gel electrophoresis, all mammalian porins show a very similar apparent molecular mass (35-35.5 kDa). In contrast yeast and Paramecium porins have a molecular mass of 30 and 37 kDa, respectively. The peptide maps of mammalian porins are very similar although small differences are apparent between porins of different tissues of the same organism and also between those of the same tissue of different organisms. The peptide patterns of porins from yeast and Paramecium are completely different from those of mammalian porins. Antibodies raised against the rat liver porin cross-react with all the other mammalian porins but not with that of yeast. The incorporation of porins into artificial lipid bilayer membranes showed that they are able to form pores with approximately the same specific activity. The single-channel conductance is for all porins, except for that of Paramecium, about 4 nS in 1 M KCl, corresponding to an effective pore diameter of 1.7 nm. They are voltage-dependent and switch to substates at transmembrane potentials higher than 10 mV. The number of gating charges varies, however, for pores from different tissues, indicating a different sensitivity to the potential as a result of a possible different function.

Adenosine Triphosphate↗
PubMed1987

Kinetics of the reconstituted 2-oxoglutarate carrier from bovine heart mitochondria.

The 2-oxoglutarate carrier from the inner membrane of bovine heart mitochondria was purified by chromatography on hydroxyapatite/celite and reconstituted with egg yolk phospholipid vesicles by the freeze-thaw-sonication technique. In the reconstituted system the incorporated 2-oxoglutarate carrier catalyzed a first-order reaction of 2-oxoglutarate/2-oxoglutarate exchange. The substrate affinity for 2-oxoglutarate was determined to be 65 +/- 18 microM (15 determinations) and the maximum exchange rate at 25 degrees C reaches 4000-22,000 mumol/min per g protein, in dependence of the particular reconstitution conditions. The activation energy of the exchange reaction is 54.3 kJ/mol. The transport is independent of pH in the range between 6 and 8. When the first fraction of the hydroxyapatite/celite column eluate was used for reconstitution, besides the 2-oxoglutarate/2-oxoglutarate exchange, a significant activity of unidirectional uptake was observed. This activity may be due to a population of the carrier protein which is in a different state.

Animals↗
PubMed1987

Photoaffinity labeling of the mitochondrial phosphate carrier by 4-azido-2-nitrophenyl phosphate.

The effect of 4-azido-2-nitrophenyl phosphate (ANPP), a photoreactive analogue of phosphate, on the phosphate carrier of pig-heart mitochondria has been investigated. In the dark, ANPP inhibits the transport of phosphate in a competitive manner with a Ki of 3.2 mM. Upon photoirradiation with visible light, [32P]ANPP binds covalently to the phosphate carrier and the inhibition becomes irreversible. Both the inhibition of phosphate transport and the incorporation of [32P]ANPP into the phosphate carrier depend on the concentration of the inhibitor and the pH of the medium. Incubation of the mitochondria with phosphate during illumination in the presence of ANPP protects the carrier against inactivation and decreases the amount of radioactivity which is found to be associated with the purified protein. By extrapolation it is calculated that at 100% inactivation of the phosphate carrier 0.35 mol of reagent are bound per mol of 33 kDa carrier protein. It is concluded that ANPP can be used for photoaffinity labeling of the mitochondrial phosphate carrier at the substrate-binding site.

Affinity Labels↗
PubMed1986

Inhibition of the mitochondrial tricarboxylate carrier by arginine-specific reagents.

The effect of arginine-specific reagents on the activity of the partially purified and reconstituted tricarboxylate carrier of the inner mitochondrial membrane has been studied. It has been found that 1,2-cyclohexanedione, 2,3-butanedione, phenylglyoxal and phenylglyoxal derivatives inhibit the reconstituted citrate/citrate exchange activity. The inhibitory potency of the phenylglyoxal derivatives increases with increasing hydrophilic character of the molecule. Citrate protects the tricarboxylate carrier against inactivation caused by the arginine-specific reagents. Other tricarboxylates, which are not substrates of the carrier, have no protective effect. The results indicate that at least one essential arginine residue is located at the substrate-binding site of the tricarboxylate carrier and that the vicinity of the essential arginine(s) has a hydrophilic character.

Animals↗
PubMed1986

Pore formation by the mitochondrial porin of rat brain in lipid bilayer membranes.

The porin of the outer membrane of rat-brain mitochondria was isolated and purified. The protein showed a single band of apparent Mr 35,500 on dodecyl sulfate-containing polyacrylamide gels. The incorporation of rat-brain porin into artificial lipid bilayer membranes showed that it is able to form pores with an average single-channel conductance of 400 pS in 0.1 M KCI. The pores were found to be voltage-dependent and switched to substrates at higher transmembrane potentials. The voltage-dependence of the rat brain pore was considerably smaller than that of the other known eukaryotic porins. The possible role of the rat-brain porin in the regulation of transport process across the outer mitochondrial membrane is discussed.

Animals↗
PubMed1985

Purification of reconstitutively active alpha-oxoglutarate carrier from pig heart mitochondria.

The alpha-oxoglutarate carrier from pig heart mitochondria has been solubilized with Triton X-114 and purified by chromatography on hydroxyapatite and celite in the presence of cardiolipin. When applied to SDS gel electrophoresis, the purified protein consists of only a single protein band with an apparent Mr of 31.5 kDa. It corresponds to band 4 of the five protein bands previously identified in the hydroxyapatite pass-through of Triton X-114 solubilized heart mitochondria (Bisaccia, F. and Palmieri, F. (1984) Biochim. Biophys. Acta 766, 386-394). When reconstituted into liposomes the alpha-oxoglutarate transport protein catalyzes a phthalonate-sensitive alpha-oxoglutarate/alpha-oxoglutarate exchange. It is purified 250-fold with a recovery of 62% and a protein yield of 0.1% with respect to the mitochondrial extract. The properties of the reconstituted carrier, i.e., the requirements for a counteranion, the substrate specificity and the inhibitor sensitivity, are similar to those described for alpha-oxoglutarate transport in mitochondria.

Animals↗
PubMed1985

The 35 kDa DCCD-binding protein from pig heart mitochondria is the mitochondrial porin.

The protein which can be labelled by low concentrations of dicyclohexylcarbodiimide in the Mr region of 30 000-35 000 has been purified from pig heart mitochondria with a high yield and as a single band of apparent Mr 35 000 in dodecyl sulphate-containing gels. The protein is not identical with the phosphate carrier as suggested before, since the two proteins behave differently during isolation. Incorporation of the isolated 35 kDa dicyclohexylcarbodiimide-binding protein into lipid bilayer membranes causes an increase of the membrane conductance in definite steps, due to the formation of pores. The specific pore-forming activity increases during the purification procedure. The single pore conductance is about 4.0 nS, suggesting a diameter of 1.7 nm of the open pore. The pore conductance is dependent on the voltage across the membrane. Anion permeability of the pore is higher than cation permeability. These properties are similar to those described for isolated mitochondrial and bacterial porins. It is concluded that the 35 kDa dicyclohexylcarbodiimide-binding protein from pig heart mitochondria is identical with porin from outer mitochondrial membrane.

Amino Acids↗