Hemitoxin (HTX) is a new K+ channel blocker isolated from the venom of the Iranian scorpion Hemis... more Hemitoxin (HTX) is a new K+ channel blocker isolated from the venom of the Iranian scorpion Hemiscorpius lepturus. It represents only 0.1% of the venom proteins, and displaces [125I]α-dendrotoxin from its site on rat brain synaptosomes with an IC50 value of 16 nm. The amino acid sequence of HTX shows that it is a 35-mer basic peptide with eight cysteine residues, sharing 29–69% sequence identity with other K+ channel toxins, especially with those of the αKTX6 family. A homology-based molecular model generated for HTX shows the characteristic α/β-scaffold of scorpion toxins. The pairing of its disulfide bridges, deduced from MS of trypsin-digested peptide, is similar to that of classical four disulfide bridged scorpion toxins (Cys1–Cys5, Cys2–Cys6, Cys3–Cys7 and Cys4–Cys8). Although it shows the highest sequence similarity with maurotoxin, HTX displays different affinities for Kv1 channel subtypes. It blocks rat Kv1.1, Kv1.2 and Kv1.3 channels expressed in Xenopus oocytes with IC50 values of 13, 16 and 2 nm, respectively. As previous studies have shown the critical role played by the β-sheet in Kv1.3 blockers, we suggest that Arg231 is also important for Kv1.3 versus Kv1.2 HTX positive discrimination. This article gives information on the structure–function relationships of Kv1.2 and Kv1.3 inhibitors targeting developing peptidic inhibitors for the rational design of new toxins targeting given K+ channels with high selectivity.
... Nature, 227 : 680-5. 17. BEN SALAH A, SAYARI A, VERGER A, GARGOURI Y (2001). Kinetic studies ... more ... Nature, 227 : 680-5. 17. BEN SALAH A, SAYARI A, VERGER A, GARGOURI Y (2001). Kinetic studies of Rhizopus oryzae lipase using monomolecular film technique. ... Biochem Biophys Acta, 530 : 227-35. 23. MOREAU H, MOULIN A, GARGOURI Y, NOEL JP, VERGER R (1991). ...
A phospholipase A2 belonging to IIA group secretory PLA2 was isolated and purified to homogeneity... more A phospholipase A2 belonging to IIA group secretory PLA2 was isolated and purified to homogeneity from the intestine of common stingray (Dasyatis pastinaca) using acidic treatment (pH 1.5) and ammonium sulphate precipitation methods combined with single-column ion-exchange chromatography. The purified enzyme was found to be a glycosylated monomeric protein with a molecular mass of about 14 kDa. The stingray sPLA2-IIA had optimum activity at 45 degrees C, unlike known mammalian PLA2-IIAs, which show optimum activity at 37 degrees C. The purified enzyme exhibited a specific activity of 290 U/mg at optimal conditions (pH 9.5 and 45 degrees C) in the presence of 6 mM NaDC and 8 mM CaCl2 with egg yolk as substrate. The NH2-terminal sequence of the enzyme and some protein fragments obtained from its tryptic digestion were also determined. All sequences obtained were similar to those of sPLA2-IIA. The enzyme also showed good stability in the presence of organic solvents, acidic and alkalin...
Toxicon : official journal of the International Society on Toxinology, Jan 15, 2014
We have purified the AaTX1 peptide from the Androctonus australis (Aa) scorpion venom, previously... more We have purified the AaTX1 peptide from the Androctonus australis (Aa) scorpion venom, previously cloned and sequenced by Legros and collaborators in a venom gland cDNA library from Aa scorpion. AaTX1 belongs to the α-Ktx15 scorpion toxins family (αKTx15-4). Characterized members of this family share high sequence similarity and were found to block preferentially IA-type voltage-dependent K(+) currents in rat cerebellum granular cells in an irreversible way. In the current work, we studied the effects of native AaTX1 (nAaTX1) using whole-cell patch-clamp recordings of IA current in substantia nigra pars compacta dopaminergic neurons. At 250 nM, AaTX1 induces 90% decrease in IA current amplitude. Its activity was found to be comparable to that of rAmmTX3 (αKTx15-3), which differs by only one conserved (R/K) amino acid in the 19th position suggesting that the difference between R19 and K19 in AaTX1 and AmmTX3, respectively, may not be critical for the toxins' effects. Molecular do...
... Nature, 227 : 680-5. 17. BEN SALAH A, SAYARI A, VERGER A, GARGOURI Y (2001). Kinetic studies ... more ... Nature, 227 : 680-5. 17. BEN SALAH A, SAYARI A, VERGER A, GARGOURI Y (2001). Kinetic studies of Rhizopus oryzae lipase using monomolecular film technique. ... Biochem Biophys Acta, 530 : 227-35. 23. MOREAU H, MOULIN A, GARGOURI Y, NOEL JP, VERGER R (1991). ...
International Journal of Biological Macromolecules, 2013
Levan polysaccharide, a type of fructan, has been shown to favorably affect diabetes type 2 and h... more Levan polysaccharide, a type of fructan, has been shown to favorably affect diabetes type 2 and hypercholesterolemia. Recent reports have indicated that excessive oxidative stress contributes to the development of atherosclerosis linked metabolic syndrome. The objective of this current study was to investigate the possible protection against oxidative stress linked atherosclerosis. A group of twenty four male rats was divided into four subgroups; a normal diet group (Control), normal rats received levan (L), a high-cholesterol diet group (Chol) and a high-cholesterol diet with 5% (w/w) levan group. After the treatment period, the plasma antioxidant enzymes and lipid profiles were determined. Our results show that treatment with levan positively changed plasma antioxidant enzyme activities by increasing superoxide dismutase (SOD) and catalase (CAT) by 40% and 28%, respectively, in heart. Similarly, the treatment of Chol fed groups with levan positively changed lipid profiles by decreasing total cholesterol, triglycerides and LDL-cholesterol by 50%, 38.33% and 64%, respectively. Thus may have potential antioxidant effects and could protect against oxidative stress linked atherosclerosis.
International Journal of Biological Macromolecules, 2013
In the present study, we have purified the group V phospholipase from the heart of cartilaginous ... more In the present study, we have purified the group V phospholipase from the heart of cartilaginous fish stingray Dasyatis pastinaca and compared its biochemical properties with group IIA (sPLA2-IIA) and IB (sPLA2-IB) phospholipases previously purified from pancreas and intestine, respectively. Group V phospholipase (sPLA2-V) was purified to homogeneity by heat treatment, ammonium sulphate precipitation and RP-HPLC. The N-terminal sequence of the purified sPLA2-V exhibits a high degree of homology with those of mammal. The enzyme was found to be monomeric with a molecular mass estimation of 14 kDa. The specific activity of the purified enzyme, measured at pH 8 and 37 °C was 52 U/mg. Like sPLA2-IB and sPLA2-IIA, the sPLA2-V is found to be stable between pH 3 and 11 after 30 min of incubation. The purified sPLA2-V retained 65% of its activity after 10 min of incubation at 70 °C and it absolutely requires Ca(2+) for enzymatic activity. In addition it displayed high tolerance to organic solvents. Kinetic parameters Kmapp, kcat and the deduced catalytic efficiency (kcat/Kmapp) of the purified group-V, -IB and -IIA PLA2s were determined using phosphatidylethanolamine (PE), phosphatidylcholine (PC) or phosphatidylserine (PS) as substrate. The three enzymes hydrolyze the zwiterionic PE and PC substrates more efficiently than anionic PS substrate.
Hemitoxin (HTX) is a new K+ channel blocker isolated from the venom of the Iranian scorpion Hemis... more Hemitoxin (HTX) is a new K+ channel blocker isolated from the venom of the Iranian scorpion Hemiscorpius lepturus. It represents only 0.1% of the venom proteins, and displaces [125I]α-dendrotoxin from its site on rat brain synaptosomes with an IC50 value of 16 nm. The amino acid sequence of HTX shows that it is a 35-mer basic peptide with eight cysteine residues, sharing 29–69% sequence identity with other K+ channel toxins, especially with those of the αKTX6 family. A homology-based molecular model generated for HTX shows the characteristic α/β-scaffold of scorpion toxins. The pairing of its disulfide bridges, deduced from MS of trypsin-digested peptide, is similar to that of classical four disulfide bridged scorpion toxins (Cys1–Cys5, Cys2–Cys6, Cys3–Cys7 and Cys4–Cys8). Although it shows the highest sequence similarity with maurotoxin, HTX displays different affinities for Kv1 channel subtypes. It blocks rat Kv1.1, Kv1.2 and Kv1.3 channels expressed in Xenopus oocytes with IC50 values of 13, 16 and 2 nm, respectively. As previous studies have shown the critical role played by the β-sheet in Kv1.3 blockers, we suggest that Arg231 is also important for Kv1.3 versus Kv1.2 HTX positive discrimination. This article gives information on the structure–function relationships of Kv1.2 and Kv1.3 inhibitors targeting developing peptidic inhibitors for the rational design of new toxins targeting given K+ channels with high selectivity.
... Nature, 227 : 680-5. 17. BEN SALAH A, SAYARI A, VERGER A, GARGOURI Y (2001). Kinetic studies ... more ... Nature, 227 : 680-5. 17. BEN SALAH A, SAYARI A, VERGER A, GARGOURI Y (2001). Kinetic studies of Rhizopus oryzae lipase using monomolecular film technique. ... Biochem Biophys Acta, 530 : 227-35. 23. MOREAU H, MOULIN A, GARGOURI Y, NOEL JP, VERGER R (1991). ...
A phospholipase A2 belonging to IIA group secretory PLA2 was isolated and purified to homogeneity... more A phospholipase A2 belonging to IIA group secretory PLA2 was isolated and purified to homogeneity from the intestine of common stingray (Dasyatis pastinaca) using acidic treatment (pH 1.5) and ammonium sulphate precipitation methods combined with single-column ion-exchange chromatography. The purified enzyme was found to be a glycosylated monomeric protein with a molecular mass of about 14 kDa. The stingray sPLA2-IIA had optimum activity at 45 degrees C, unlike known mammalian PLA2-IIAs, which show optimum activity at 37 degrees C. The purified enzyme exhibited a specific activity of 290 U/mg at optimal conditions (pH 9.5 and 45 degrees C) in the presence of 6 mM NaDC and 8 mM CaCl2 with egg yolk as substrate. The NH2-terminal sequence of the enzyme and some protein fragments obtained from its tryptic digestion were also determined. All sequences obtained were similar to those of sPLA2-IIA. The enzyme also showed good stability in the presence of organic solvents, acidic and alkalin...
Toxicon : official journal of the International Society on Toxinology, Jan 15, 2014
We have purified the AaTX1 peptide from the Androctonus australis (Aa) scorpion venom, previously... more We have purified the AaTX1 peptide from the Androctonus australis (Aa) scorpion venom, previously cloned and sequenced by Legros and collaborators in a venom gland cDNA library from Aa scorpion. AaTX1 belongs to the α-Ktx15 scorpion toxins family (αKTx15-4). Characterized members of this family share high sequence similarity and were found to block preferentially IA-type voltage-dependent K(+) currents in rat cerebellum granular cells in an irreversible way. In the current work, we studied the effects of native AaTX1 (nAaTX1) using whole-cell patch-clamp recordings of IA current in substantia nigra pars compacta dopaminergic neurons. At 250 nM, AaTX1 induces 90% decrease in IA current amplitude. Its activity was found to be comparable to that of rAmmTX3 (αKTx15-3), which differs by only one conserved (R/K) amino acid in the 19th position suggesting that the difference between R19 and K19 in AaTX1 and AmmTX3, respectively, may not be critical for the toxins' effects. Molecular do...
... Nature, 227 : 680-5. 17. BEN SALAH A, SAYARI A, VERGER A, GARGOURI Y (2001). Kinetic studies ... more ... Nature, 227 : 680-5. 17. BEN SALAH A, SAYARI A, VERGER A, GARGOURI Y (2001). Kinetic studies of Rhizopus oryzae lipase using monomolecular film technique. ... Biochem Biophys Acta, 530 : 227-35. 23. MOREAU H, MOULIN A, GARGOURI Y, NOEL JP, VERGER R (1991). ...
International Journal of Biological Macromolecules, 2013
Levan polysaccharide, a type of fructan, has been shown to favorably affect diabetes type 2 and h... more Levan polysaccharide, a type of fructan, has been shown to favorably affect diabetes type 2 and hypercholesterolemia. Recent reports have indicated that excessive oxidative stress contributes to the development of atherosclerosis linked metabolic syndrome. The objective of this current study was to investigate the possible protection against oxidative stress linked atherosclerosis. A group of twenty four male rats was divided into four subgroups; a normal diet group (Control), normal rats received levan (L), a high-cholesterol diet group (Chol) and a high-cholesterol diet with 5% (w/w) levan group. After the treatment period, the plasma antioxidant enzymes and lipid profiles were determined. Our results show that treatment with levan positively changed plasma antioxidant enzyme activities by increasing superoxide dismutase (SOD) and catalase (CAT) by 40% and 28%, respectively, in heart. Similarly, the treatment of Chol fed groups with levan positively changed lipid profiles by decreasing total cholesterol, triglycerides and LDL-cholesterol by 50%, 38.33% and 64%, respectively. Thus may have potential antioxidant effects and could protect against oxidative stress linked atherosclerosis.
International Journal of Biological Macromolecules, 2013
In the present study, we have purified the group V phospholipase from the heart of cartilaginous ... more In the present study, we have purified the group V phospholipase from the heart of cartilaginous fish stingray Dasyatis pastinaca and compared its biochemical properties with group IIA (sPLA2-IIA) and IB (sPLA2-IB) phospholipases previously purified from pancreas and intestine, respectively. Group V phospholipase (sPLA2-V) was purified to homogeneity by heat treatment, ammonium sulphate precipitation and RP-HPLC. The N-terminal sequence of the purified sPLA2-V exhibits a high degree of homology with those of mammal. The enzyme was found to be monomeric with a molecular mass estimation of 14 kDa. The specific activity of the purified enzyme, measured at pH 8 and 37 °C was 52 U/mg. Like sPLA2-IB and sPLA2-IIA, the sPLA2-V is found to be stable between pH 3 and 11 after 30 min of incubation. The purified sPLA2-V retained 65% of its activity after 10 min of incubation at 70 °C and it absolutely requires Ca(2+) for enzymatic activity. In addition it displayed high tolerance to organic solvents. Kinetic parameters Kmapp, kcat and the deduced catalytic efficiency (kcat/Kmapp) of the purified group-V, -IB and -IIA PLA2s were determined using phosphatidylethanolamine (PE), phosphatidylcholine (PC) or phosphatidylserine (PS) as substrate. The three enzymes hydrolyze the zwiterionic PE and PC substrates more efficiently than anionic PS substrate.
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