T lymphocytes possess receptors for brain myelin small protein

In immunomediated demyelinating diseases, T cells are found in chronic lesions. To discover whether immunocompetent cells may interact with some myelin proteins, we purified myelin proteins in the lipid-bound native state and evaluated their binding to peripheral blood mononuclear cells (PMBC) isolated from healthy donors. To this end, myelin proteins were conjugated to biotin and added to PBMCs or purified CD4+ and CD8+ cells; then binding was detected using fluoresceinated avidin. In this article, we describe experiments carried out with a myelin protein recently discovered in the central nervous system. Our results show that this small, phosphatidylserine-binding protein can bind to human T cells.

[Bronchogenic cysts of the mediastinum]

The case of a bronchial cyst found on the mediastinal carina whose early symptoms resulted from compression of the airways is reported. The clinical, pathogenic and diagnostic aspects of these often congenital cystic malformations of the mediastinum are discussed.

[Evaluation of the operative risk of gastric tumor surgery at an advanced age. Retrospective study]

A retrospective study was carried out in 41 over-70 year-olds who had been operated on for gastric cancer in 1984-86 at the General Surgery Division of Imola to see if age is an unfavourable prognostic factor in this situation. Age was not decisive in surgical results. Operative mortality is correlated with the degree of operative risk expressed on the basis of an analysis of the patient's biological state prior to the operation and of the specific and aspecific effects of surgery.

Fluorescence spectral resolution of myelin basic protein conformers in complexes with lysophosphatidylcholine

The structure of (Deibler) myelin basic protein in solution and in a lysolecithin++ lipid complex has been studied by using the emission properties of the single tryptophan residue of the protein (Trp-115). The studies have been carried out using both static and time-resolved fluorescence techniques. Relative to the free protein, the lipid bound myelin basic protein showed a twofold increase in fluorescence intensity and a marked blue-shift in the emission maximum wavelength. The multiexponential fluorescence decays and the decay associated spectra indicated that the protein exists in at least three different conformations both in buffer and in lipids. Fluorescence polarization and acrylamide quenching experiments showed that the tryptophan containing region of the protein is embedded in the lipid matrix. The binding of the protein to the lipid appears to be comparable with that predicted for the interaction of amphipathic helices with nonpolar lipids.

Myelin basic protein ability to organize lipid bilayers: structural transition in bilayers of lysophosphatidylcholine micelles

Myelin basic protein isolated by a single step with the cationic detergent cethyltrimethylammonium bromide in a lipid-bound form is able to induce structural transition of lysophosphatydilcholine micelles into multi-laminar vesicles. This finding, observed through electron microscopy, is discussed in the light of the assumed ability of the basic protein to organize myelin lipids.

A new protein of the brain myelin: isolation and chemical characterization

An unknown protein has been isolated from bovine brain myelin. This protein, purified in the nonionic detergent n-octylpolydisperse oligooxyethylene, reveals on SDS gel electrophoresis a large number of bands in the higher MW region. However, chemical analysis and gel chromatography indicate the presence of a single, small protein containing large amounts of bound phosphatidylserine. N-terminal and C-terminal sequences, aminoacid composition, and the anomalous electrophoretic behaviour led us to exclude the protein as a fragment of other already known myelin proteins.

On the binding of brain myelin basic protein to chromatographic resins

Myelin basic protein, only in association with certain detergents, is able to bind irreversibly to the usual gel filtration media. While this binding is greatly advantageous in purification of proteolipid (the other major myelin protein), the question arises of the uncommon, nonphysiological behaviour of the basic protein. A relationship between binding property and basic protein structure is suggested.

A new procedure for the isolation of the brain myelin basic protein in a lipid-bound form

Myelin basic protein has been isolated from bovine brain using the nonionic detergent n-octyl-polydisperse oligooxyethylene. The purified basic protein contains large amounts of heterogeneous lipids.

[Interaction of 3-(3H)-2-n-nonyl-4-hydroxyquinoline-N-oxide with submitochondrial particles of beef heart. III. Correlation between the binding of 3H-NQNO and inhibition of the respiratory activity]

The present work is an extension of our precedent papers (1-3). In the present report the relationship was studied between the inhibition by 3H-NQNO, 3-3H-2-n-nonyl-4-hydroxy-quinoline-N-oxide, of the respiratory activity induced in submitochondrial particles from beef heart by NADH and the binding of 3H-NQNO to the specific binding site. The experiments showed that the concentrations of inhibition sites and of specific binding sites are identical. Titrating the inhibition of NADH-oxidase activity with increasing amounts of 3H-NQNO a close connection was observed between the decrease of the respiratory activity and the increase of the specific binding of 3H-NQNO. When nearly full inhibition (85%) was reached, also the specific binding was saturated. We may conclude that 3H-NQNO behaves like an ideally simple inhibitor: the inhibition of electron transfer by 3H-NQNO is linear with the saturation of the specific binding site.

[Interaction of 3-[3H]-2-n-nonyl-4-hydroxyquinoline-N-oxide with submitochondrial particles of beef heart. II. Determination of the binding sites]

The binding of 3H-NQNO in submitochondrial particles was determined by measuring the radioactivity in the supernatants as well as in the sediments after centrifugation of particles suspensions containing different amounts of 3H-NQNO. From the binding data Scatchard plots were constructed showing a large amount of aspecific binding depending on the particles preparation and concentration. In the presence of saturating concentrations of either antimycin or unlabelled NQNO (2-n-Nonyl-4-hydroxy-quinolinee-N-oxide) that remove or prevent the specific binding of 3H-NQNO, it is possible to evaluate the aspecific component of 3H-NQNO binding and to subtracte it from the experimental binding data by graphyc correction according to (3). The straight line from the corrected points gives the specific binding parameters: number of specific binding sites: about 0,5 moles 3H-NQNO/ moles cytochrome b and KD= 50 nM.

[Interaction of 3-[3H]-2-n-nonyl-4-hydroxy-quinoline-N-oxide with submitochondrial particles of beef heart. I. Inhibition of the respiratory activity]

The inhibitory effect of 3-3H-2-n-nonyl-4-hydroxy-quinoline-N-oxide (3H-NQNO) on the respiration induced by NADH or by succinate was studied in submitochondrial particles from beef heart. Polarographic experiments showed that oxygen uptake by submitochondrial particles was inhibited by 3H-NQNO. Similar results were obtained with the unlabelled compound NQNO. The inhibitory activity of 3H-NQNO on the respiration was 2 or 3 times better than that of the heptyl derivatives (HQNO) and additive with that shown by antimycin.

Isolation of the ADP, ATP carrier as the carboxyatractylate . protein complex from mitochondria

The procedure for the isolation from mitochondria of the undenatured ADP, ATP carrier is described. The condition of retaining the nativity are elaborated. 1. As indicator for the ADP, ATP carrier (35S)- or (3H) carboxyatractylate were used. By preloading the mitochondria with carboxyatractylate, a stable carboxyatractylate . protein complex could be retained after solubilization with Triton X-100. Among the polyoxyethylene detergents emulphogen is also solubilizing, whereas Brij and Lubrol fail to solubilize. 2. When unloaded mitochondria are solubilized the capacity for binding carboxyatractylate disappears rapidly, particularly at 20 degrees C. 3. When mitochondria are preloaded with atractylate, the binding after solubilization with Triton X-100 is considerably lower than with carboxyatractylate, indicating that the high affinity of carboxyatractylate is required for effectively protecting the protein. 4. For purification hydroxyapatite is most effective. The carboxyatractylate-protein complex appears in the pass-through whereas the bulk of other mitochondrial proteins are retained such that a 7-fold purification is obtained. The nonadsorptivity to hydroxyapatite is dependent on the undenatured state maintained in the carboxyatractylate . protein complex. 5. Subsequent gel filtration on Sepharose results in a 1.5-fold further enrichment of specific carboxyatractylate binding up to 17 mumol/g protein, corresponding to a 10-fold purification from mitochondria. This value cannot be increased with further measures. 6. At the last purification step, in sodium dodecyl sulfate polyacrylamide gel electrophoresis virtually a single band of 30 000 molecular weight is found, confirming the purity at this stage. A molecular weight of 60 000 is calculated from the carboxyatractylate binding, indicating that the carboxyatractylate protein complex consists of two 30 000 subunits. From this the protein share of the ADP, ATP carrier in beef heart mitochondria can be calculated to amount to 9.5%9 7. The intact carboxyatractylate . protein complex is protected against proteolytic degradation. The release of carboxyatractylate ensues a conformational change of protein as assayed by conformation specific antibodies, concomitant with unmasking of proteolytic site as assayed by tryptic digestion. 8. The amino acid composition indicates hydrophobicity (39% polarity) and a high content of basic amino acid such as lysine and arginine. There is 1.5 mol percent cysteine and a blocked N-terminal. 9. From the solubilized complex (35S) carboxyatractylate can be removed by carboxyatractylate, ADP and ATP but not by ITP, etc., indicating the presence of recognizing sites specific fof ADP, ATP and therefore, identity with the ADP, ATP carrier. 10. Other reported procedures for isolating the ADP, ATP carrier are shown to either fail or have lower yield than the present, original procedure.

The biosynthesis of the mitochondrial ADP, ATP translocator

The biosynthesis of the ADP,ATP carrier was studied in mitochondria of Neurospora crassa. The carrier was isolated as the carboxyatractylate-protein complex and characterized in dodecylsulphate/polyacrylamide gel electrophoresis to have a Mr = 33 000. Applying the inhibitors chloramphenicol for the intramitochondrial translation and cycloheximide for extramitochondrial translation, the site of synthesis of this polypeptide was found to be extramitochondrially located.

bc1-Complex from beef heart. One-step purification by hydroxyapatite chromatography in Triton X-100, polypeptide pattern and respiratory chain characteristics

A new simple method for the purification of the bc1-complex has been developed. The polypeptide composition of the complex was analysed by dodecyl sulfate-polyacrylamide gel electrophoresis. The content of chain components and phospholipids was determined. The b-type cytochromes were further characterized by their absorbance spectra and midpoint potentials. (1) Starting from a Triton X-100 extract of submitochondrial particles supplemented with antimycin, the bc1-complex is purified by adsorption chromatography on hydroxyapatite with citrate as specific eluant. (2) The complex splits in dodecyl sulfate into five main polypeptides with apparent molecular weight of 47, 44, 31, 11 and less than 10 kdalton. (3) The purified complex has a heme-b content of 8.0 mumol/g protein and a cytochrome c1 content of 3.8 mumol/g protein. (4) The cytochromes show the typical absorbance spectra of cytochromes b-562 and b-565 and are present in approximately equal amounts with midpoint potentials of Em7 = + 100 mV and Em7 = + mV respectively. Carbon monoxide does not bind to the cytochromes. (5) The nonheme iron protein content of the complex is diminished to 0.6 mumol/g protein. (6) The use of the nonionic surfactant Triton X-100 leads to a complete loss of lipids and ubiquinone of the bc1-complex. (7) The complex contains no succinate dehydrogenase as indicated by the absence of the 69 kdalton subunit in the dodecyl sulfate gel electrophoresis. In addition, it lacks an ubiquinone cytochrome c reductase activity and other electron transferring activities. This may be inferred from an inhibition by antimycin and depletion of ubiquinone and phospholipids. The highly purified and relative stable complex can be prepared giving 50% yield and may be suitable for protein chemistry studies.

Antibody evidence for different conformational states of ADP, ATP translocator protein isolated from mitochondria

Consistent with the previously proposed reorientation mechanism for the ADP,ATP translocator protein of mitochondria, evidence has now been obtained for the existence of two distinct conformational states of the isolated translocator protein. Previous studies indicated that when the mitochondrial translocator protein is in the c-state(i.e., when its binding site faces the cytosol side) the protein binds primarily the ligand carboxyatractylate (CAT), and when the translocator protein is in the m-state(i.e., when its binding site faces the mitochondrial matrix) the translocator protein binds primarily bongkrekate. Direct evidence for this formulation has now come from the application of antibodies to the isolated translocator protein-ligand complex. Two antibodies were produced against the ADP,ATP translocator protein isolated from beef heart mitochondria. One antibody, which was produced against the protein isolated as the CAT-binding protein complex, was found to be highly specific for that complex and did not react with the protein in the conformation state conferred by the bongkrekate ligand. This antibody did not cover the CAT-binding site, as evidenced by the exchange of unlabeled CAT with [35S]CAT bound to the translocator protein. However, the same antibody inhibited a transition of the protein from the c-state to the m-state, as evidenced by an inhibition of the displacement of[35S]CAT by bongkrekate (added jointly with ADP). It appears, therefore, that the antibody immobilized the translocator protein in the c-state. The second antibody produced against the (somewhat less pure) ADP,ATP translocator protein, isolated as the bongkrekate-binding protein complex, did not react with the CAT-binding protein. Thus, the second antibody appeared to be specific for the translocator protein in the m-state. Neither antibody inhibited mitochondrial ADP,ATP transport.