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T Rabilloud

Publications and source records attributed to T Rabilloud.

At least 37 records · Page 2Linked to original sources
PubMed1998

Use of thiourea to increase the solubility of membrane proteins in two-dimensional electrophoresis.

The separation of membrane proteins by high-resolution two-dimensional electrophoresis was carried out. At high loads, these proteins are prone to precipitation, resulting in poor resolution. It is shown here that the use of thiourea, previously described for focusing in immobilized pH gradients, can be extended to conventional isoelectric focusing. As thiourea inhibits acrylamide polymerization, a modified photopolymerization system must be used. These modifications result in higher solubility of proteins during IEF, thereby increasing the resolution and capacity of the two-dimensional gels.

Cell Line↗
PubMed1998

Two-dimensional electrophoresis of human placental mitochondria and protein identification by mass spectrometry: toward a human mitochondrial proteome.

Owing to the complexity of higher eukaryotic cells, characterization of a complete proteome is likely to be difficult to achieve. However, advantage can be taken of the cell compartmentalization to build organelle proteomes, which can moreover be viewed as specialized tools to study specifically the biology and "physiology" of the target organelle. Within this frame, we report here the construction of the human mitochondrial proteome, using placenta as the source tissue. Protein identification was carried out mainly by peptide mass fingerprinting, but other methods were also used (N-terminal microsequencing, blotting). The optimization steps in two-dimensional (2-D) electrophoresis needed for proteome research are discussed. However, the relative paucity of data concerning mitochondrial proteins is still the major limiting factor in building the corresponding proteome, which should be a useful tool for researchers working on human mitochondria and their deficiencies.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1998

New zwitterionic detergents improve the analysis of membrane proteins by two-dimensional electrophoresis.

Severe quantitative loss of protein is often observed in high-resolution two-dimensional electrophoresis of membrane proteins, while the resolution is usually not affected. To improve the solubility of proteins in this technique, we tested denaturing cocktails containing various detergents and chaotropes. Best results were obtained with a denaturing solution containing urea, thiourea, and zwitterionic detergents, synthesized for this purpose. Among the dozen detergents synthesized and tested, amidosulfobetaines with an alkyl tail containing 14-16 carbons proved most efficient, solubilizing previously undetected membrane proteins.

Animals↗
PubMed1998

Use of ethanolamine for sample stacking in capillary electrophoresis.

Capillary zone electrophoresis (CZE) in the presence of ethanolamine was used in a micropreparative mode. Sample volumes up to 1 microL could be loaded onto a 100 microns diameter capillary without loss in resolution. Coupled to narrow-bore reversed-phase high-performance liquid chromatography, ethanolamine-CZE allowed the collection of sufficient amounts of pure peptidic material to perform amino acid sequence analysis.

Amino Acid Sequence↗
PubMed1997

Functional properties of the separate subunits of human DNA helicase II/Ku autoantigen.

The Ku antigen consists of two subunits of 70 and 83 kDa and is endowed with both duplex DNA end-binding capacity and helicase activity (human DNA helicase II). HeLa Ku can be isolated from in vitro cultured human cells uniquely as a heterodimer, and the subunits can be separated by electrophoresis only under denaturing conditions. To dissect the molecular functions of the two subunits of the heterodimer, we have cloned and expressed their cDNAs separately in Escherichia coli. The two activities of Ku (DNA binding and unwinding) were reconstituted by mixing and refolding both subunits in equimolar amounts (Tuteja, N., Tuteja, R., Ochem, A., Taneja, P., Huang, N-W., Simoncsits, A., Susic, S., Rahman, K., Marusic, L., Chen, J., Zang, J., Wang, S., Pongor, S., and Falaschi, A. (1994) EMBO J. 13, 4991-5001). Renaturation of the separate subunits can be achieved in the presence of a synthetic solubilizing and stabilizing agent, dimethyl ethylammonium propane sulfonate (NDSB 195). The helicase activity of the Ku protein resides uniquely in the 70-kDa subunit, whereas the DNA end-binding activity can be reconstituted only through renaturation of the two subunits in the heterodimeric form and is practically absent in the separate subunits. The 83-kDa subunit, when refolded in the absence of the 70-kDa subunit, forms homodimers unable to unwind DNA and bind duplex ends. The three separate species (heterodimer, 70-kDa subunit, and 83-kDa subunit homodimer) all have ssDNA-dependent ATPase activity.

Adenosine Triphosphatases↗
PubMed1997

The 40-kDa component of the phagocyte NADPH oxidase (p40phox) is phosphorylated during activation in differentiated HL60 cells.

The superoxide-generating NADPH oxidase complex of phagocytic cells is a multicomponent system containing a membrane-bound flavocytochrome b and a small G protein Rac as well as cytosolic factors p67phox, p47phox and p40phox which translocate to the membrane upon activation. Known mechanisms underlying the translocation of these proteins include polyphosphorylation of p47phox and specific Src homology 3/polyproline motif interactions. In this study, through two-dimensionnal electrophoresis and immunoprecipitation experiments, we show using dimethylsulfoxide-differentiated HL60 promyelocytes that p40phox is in a basal phosphorylated state in resting cells and undergoes further phosphorylation on multiple sites upon stimulation of the NADPH oxidase by either phorbol myristate acetate or by the formyl peptide fMet-Leu-Phe-Lys. Moreover, the extent of phosphorylation is strongly correlated with the level of superoxide production. Typically, in cells transiently activated by fMet-Leu-Phe-Lys, onset of superoxide production coincides with the appearance of new phosphorylated species of p40phox and, at the end of the respiratory burst, dephosphorylation of p40phox is observed. In vitro assays show that the kinase(s) involved in the phosphorylation of p40phox differ from those which participate in the phosphorylation of p47phox. This suggests that, in the cell, the phosphorylation of p40phox and of p47phox are under the control of two different kinase pathways.

Cell Differentiation↗
PubMed1997

A nonradioactive double detection method for the assignment of spots in two-dimensional blots.

A method for identification of spots on two-dimensional electrophoresis gels by means of immunoblotting is described. This method does not require radioactive-labeled proteins and is based on the dual use of colloidal gold staining to detect the general 2D pattern on the blot and on chemiluminescence to detect the antibody-reactive spot(s). Profit is taken from the fact that the general gold stain produces a background pattern on strong ECL exposures, which allows alignment of the antibody-reactive spot(s) on the general pattern and therefore easy identification of the spot(s) of interest on the two-dimensional maps.

Bacterial Proteins↗
PubMed1997

Regulation of protein phosphatase 2A by direct interaction with casein kinase 2alpha.

Timely deactivation of kinase cascades is crucial to the normal control of cell signaling and is partly accomplished by protein phosphatase 2A (PP2A). The catalytic (alpha) subunit of the serine-threonine kinase casein kinase 2 (CK2) bound to PP2A in vitro and in mitogen-starved cells; binding required the integrity of a sequence motif common to CK2alpha and SV40 small t antigen. Overexpression of CK2alpha resulted in deactivation of mitogen-activated protein kinase kinase (MEK) and suppression of cell growth. Moreover, CK2alpha inhibited the transforming activity of oncogenic Ras, but not that of constitutively activated MEK. Thus, CK2alpha may regulate the deactivation of the mitogen-activated protein kinase pathway.

3T3 Cells↗
PubMed1997

Two-dimensional electrophoresis of membrane proteins: a current challenge for immobilized pH gradients.

Membrane proteins were separated by high resolution two-dimensional (2-D) electrophoresis. On isoelectric focusing (IEF) with immobilized pH gradients severe protein losses in the resulting 2-D map were observed when compared with carrier ampholyte-based IEF. This has been noticed for two different biological systems, namely the chloroplast envelope of spinach and the endocytic vesicles from Dictyostelium discoideum. The possible mechanisms of these losses on immobilized pH gradients are discussed.

Animals↗
PubMed1996

One- and two-dimensional histone separations in acidic gels: usefulness of methylene blue-driven photopolymerization.

We tested the recently introduced methylene blue-toluene sulfinate-diphenyl-iodonium polymerization system in order to prepare acetic acid-urea-Triton X-100 gels for histone separations. When compared to standard persulfate-based initiators, this system exhibited several advantages. First, the polymerization proceeds at a much faster rate but is easily controlled since it is light-dependent. Second, no prerunning of the gel was required, since there is no oxidizing molecule able to introduce artifacts. Moreover, this procedure produces gels presenting cleaner backgrounds with silver staining. The ability of the procedure to carry out high resolution two-dimensional electrophoresis of histones was also examined. High resolution two-dimensional gels, using photopolymerized acidic gels as the first or second dimension were obtained.

Acetic Acid↗
PubMed1996

Non-detergent sulphobetaines: a new class of molecules that facilitate in vitro protein renaturation.

BACKGROUND: Attempts to renature proteins often yield aggregates rather than native protein. To minimize aggregation, low protein concentrations and/or solubilizing agents are used. Here, we test new solubilizing molecules, non-detergent sulphobetaines, to improve the renaturation of two very different enzymes, hen egg white lysozyme and bacterial beta-D-galactosidase. RESULTS: The renaturation was conducted in the presence of five different sulphobetaines and the yield of active enzyme was measured. The five sulphobetaines improved the yield of native lysozyme up to 12-fold. Some sulphobetaines improved the yield of galactosidase up to 80-fold, but one reduced it 100-fold. CONCLUSIONS: Non-detergent sulphobetaines strongly affect the balance between aggregation and folding. Their effect depends on their structure and on their interactions with folding intermediates. These results should serve as a basis for designing more efficient sulphobetaines; for designing improved renaturation protocols using existing sulphobetaines; and for characterizing folding intermediates that interact with sulphobetaines.

Animals↗
PubMed1995

Early events in erythroid differentiation: accumulation of the acidic peroxidoxin (PRP/TSA/NKEF-B).

The acidic peroxidoxin [also named thiol-specific antioxidant protein (TSA) or protector protein (PRP)], which plays a role in the response against oxidative stress, is one of the major proteins of red blood cells. In this work, we show that this protein is induced at early stages of erythroid differentiation prior to haemoglobin accumulation, which suggests that it may play a role at the erythroblast stage, where haemoglobinized, nucleated and genetically active cells are submitted to a maximally dangerous oxidative stress. The early accumulation of this protein has been demonstrated both on transformed cell systems and on normal differentiating human erythroid cells. This suggests that this protein may play an important role in the differentiation of the erythroid cells.

Animals↗
PubMed1995

Halophilic protein stabilization by the mild solubilizing agents nondetergent sulfobetaines.

In this work, experiments performed on pig heart and halophilic malate dehydrogenase as well as halophilic elongation factor Tu demonstrate a protein stabilization property from the recently described mild solubilizing agents nondetergent sulfobetaines. A practical application is given by the separation of halophilic bacteria elongation factor Tu and halophilic malate dehydrogenase by high-performance ion-exchange chromatography achieved at reduced salt levels without significant loss of activity.

Animals↗
PubMed1995

Non-detergent sulphobetaines: a new class of mild solubilization agents for protein purification.

The action of non-detergent sulphobetaines (NDSBs) as new mild agents for protein purification is described. The solubilization effects of non-detergent sulphobetaines are shown in different examples; all obtained under non-denaturing conditions: (1) microsomal proteins extraction; (2) recovery after dialysis of nuclear proteins; (3) reduction of precipitation in isoelectric focusing experiments under non-denaturing conditions; and (4) purification of a membrane-bound serine protease from Plasmodium falciparum involved in erythrocyte invasion by malaria merozoites. The absence of a significant denaturation effect induced by NDSBs is demonstrated by tests on beta-galactosidase and alkaline phosphatase. A simple NDSB synthesis and some possible explanations of the action of NDSBs are also presented.

Animals↗
PubMed1995

Micropreparative one- and two-dimensional electrophoresis: improvement with new photopolymerization systems.

To improve the efficiency of one- and two-dimensional electrophoresis for micropreparative purposes, the use of gels polymerized with other initiators than the standard N,N,N',N'-tetramethylethylenediamine (TEMED)/persulfate systems for sodium dodecyl sulfate electrophoresis has been investigated. We show here that the recently described photoinitiator system, composed of methylene blue, toluene sulfinate and diphenyliodonium chloride, leads to a decreased resolution. Resolution can be restored if methylene blue is replaced by riboflavin. Two-dimensional electrophoresis with mg loadings of proteins has also been evaluated with these systems. Independently of the polymerization system, resolution for the first dimension is low with rod gels, increases with gel strips and is further improved when immobilized pH gradients are used. Here too, only the riboflavin/sulfinate/iodonium system results in a resolution that matches the one obtained with the standard TEMED/persulfate system. Gels polymerized with the riboflavin/sulfinate/iodonium system yield better results upon N-terminal microsequencing after blotting than gels polymerized with the standard TEMED/persulfate system.

Ammonium Sulfate↗
PubMed1995

Enhancing protein solubilization with nondetergent sulfobetaines.

A significant increase in the yield of protein extraction by the addition of sulfobetaine-type mild solubilization agents is shown for microsomal membrane proteins and proteins from lyophilized platelets, with a maximum increase in yield of up to 100%. These agents are also applied to native isoelectric focusing in immobilized pH gradients. The absence of significant denaturation induced by these solubilizers is shown for creatine kinase.

Animals↗