Amor Mosbah - Academia.edu (original) (raw)
Papers by Amor Mosbah
Biochemistry, 2001
Ptu1 is a toxin from the assassin bug Peirates turpis which has been demonstrated to bind reversi... more Ptu1 is a toxin from the assassin bug Peirates turpis which has been demonstrated to bind reversibly the N-type calcium channels and to have lower affinity than the omega-conotoxin MVIIA. We have determined the solution structure of Ptu1 by use of conventional two-dimensional NMR techniques followed by distance-geometry and molecular dynamics. The calculated structure of Ptu1 belongs to the inhibitory cystin knot structural family (ICK) that consists of a compact disulfide-bonded core from which four loops emerge. Analysis of the 25 converged solutions indicates that the molecular structure of Ptu1 contains a 2-stranded antiparallel beta-sheet (residues 24-27 and 31-34) as the only secondary structure. The loop 2 that has been described to be critical for the binding of the toxin on the channel is similar in Ptu1 and MVIIA. In this loop, the critical residue, Tyr13, in MVIIA is retrieved in Ptu1 as Phe13, but the presence of an acidic residue (Asp16) in Ptu1 could disturb the binding of Ptu1 on the channel and could explain the lower affinity of Ptu1 toward the N-type calcium channel compared to the one of MVIIA. Analysis of the electrostatic charge's repartition gives some insights about the importance of the basic residues, which could interact with acidic residues of the channel and then provide a stabilization of the toxin on the channel.
European Journal of Biochemistry
A group of ubiquitous small proteins (average 13 kDa) has been isolated from several sensory orga... more A group of ubiquitous small proteins (average 13 kDa) has been isolated from several sensory organs of a wide range of insect species. They are believed to be involved in chemical communication and perception (olfaction or taste) and have therefore been called chemo-sensory proteins (CSPs). Several CSPs have been identified in the antennae and proboscis of the moth Mamestra brassicae. We have expressed one of the antennal proteins (CSPMbraA6) in large quantities as a soluble recombinant protein in Escherichia coli periplasm. This 112-residue protein is a highly soluble monomer of 13 072 Da with a pI of 5.5. NMR data (1H and 15N) indicate that CSPMbraA6 is well folded and contains seven alpha helices (59 amino acids) and two short extended structures (12 amino acids) from positions 5 to 10 and from 107 to 112. Thirty-seven amino acids are involved in beta turns and coiled segments and four amino acids are not assigned in the NMR spectra (the N-terminus and the residue 52 in the loop ...
Journal of Biomolecular NMR
Staphylococcus aureus produces peptide toxins that it uses to respond to environmental cues. We p... more Staphylococcus aureus produces peptide toxins that it uses to respond to environmental cues. We previously characterized PepA1, a peptide toxin from S. aureus, that induces lytic cell death of both bacterial and host cells. That led us to suggest that PepA1 has an antibacterial activity. Here, we demonstrate that exogenously provided PepA1 has activity against both Gram-positive and Gram-negative bacteria. We also see that PepA1 is significantly hemolytic, thus limiting its use as an antibacterial agent. To overcome these limitations, we converted PepA1 into nonhemolytic derivatives. Our most promising derivative is a cyclic heptapseudopeptide with inconsequential toxicity to human cells, enhanced stability in human sera, and sharp antibacterial activity. Mechanistically, linear and helical PepA1 derivatives form pores at the bacterial and erythrocyte surfaces, while the cyclic peptide induces bacterial envelope reorganization, with insignificant action on the erythrocytes. Our work...
The viral broad spectrum chemokine vCCL2 binds to the chemokine receptors CXCR4 and CCR5 and inhi... more The viral broad spectrum chemokine vCCL2 binds to the chemokine receptors CXCR4 and CCR5 and inhibits HIV-1 entry protecting host cells against infection [1]. Peptide derived from vCCL2 N-terminus (vCCL2 1-21) displays modest CXCR4 and CXCR7 binding affinity and antiviral properties compared to the parental chemokine but mutations within its CC motif has been shown to enhance its antiviral properties, for review see [2]. In this study, we exploited these observations to develop highly potent and selective CXCR4 antagonists. The aim of the current study was to develop a new class of short and selective CXCR4 inhibitors inspired by the binding mode of natural chemokines (Mimokines). The N-terminus of vCCL2 (vCCL2 (1-21)), a viral chemokine displaying antagonist properties on CXCR4, was used as scaffold to introduce controlled randomizations and to create phage library of peptide variants. A Mimokine phage display library, in which C 11 C 12 amino acids within the N-terminus vCCL2 (1-2...
The Journal of biological chemistry, Jan 21, 2001
Polysaccharide-degrading enzymes are generally modular proteins that contain non-catalytic carboh... more Polysaccharide-degrading enzymes are generally modular proteins that contain non-catalytic carbohydrate-binding modules (CBMs), which potentiate the activity of the catalytic module. CBMs have been grouped into sequence-based families, and three-dimensional structural data are available for half of these families. Clostridium thermocellum xylanase 11A is a modular enzyme that contains a CBM from family 6 (CBM6), for which no structural data are available. We have determined the crystal structure of this module to a resolution of 2.1 A. The protein is a beta-sandwich that contains two potential ligand-binding clefts designated cleft A and B. The CBM interacts primarily with xylan, and NMR spectroscopy coupled with site-directed mutagenesis identified cleft A, containing Trp-92, Tyr-34, and Asn-120, as the ligand-binding site. The overall fold of CBM6 is similar to proteins in CBM families 4 and 22, although surprisingly the ligand-binding site in CBM4 and CBM22 is equivalent to cleft...
Chemistry & Biology, 2015
European Journal of Biochemistry, 2001
Peptides, 2004
Alpha scorpion toxins bind to receptor site 3 on voltage-dependent sodium channels and inhibit th... more Alpha scorpion toxins bind to receptor site 3 on voltage-dependent sodium channels and inhibit their inactivation. The α-scorpion toxin BotIII is the most toxic protein of Buthus occitanus tunetanus. Its sequence differs only by three amino acid residues from that of AahII, the most active α-toxin. Due to their high affinity and selectivity for mammalian sodium channels, BotIII and AahII
European Journal of Biochemistry, 2003
Proteins: Structure, Function, and Genetics, 2000
Proteins: Structure, Function, and Bioinformatics, 2005
Pathophysiology of Haemostasis and Thrombosis, 2001
Lebetins from Macrovipera lebetina snake venom constitute a new class of inhibitors of platelet a... more Lebetins from Macrovipera lebetina snake venom constitute a new class of inhibitors of platelet aggregation. There are two groups of peptides: lebetin 1 (L1; 11- to 13-mer) and lebetin 2 (L2; 37- to 38-mer). The short lebetins are identical to the N-terminal segments of the longer ones. They inhibit platelet aggregation induced by various agonists (e.g. thrombin, PAF-acether or collagen). The shortest lebetin (11-mer) shows potent inhibition of rabbit (IC(50) = 7 nM) and human (IC(50) = 5 nM) platelets. They prevent collagen-induced thrombocytopenia in rats. N- and C-terminal-truncated synthetic L1gamma (sL1gamma; 11-mer) is less active in inhibiting platelet aggregation than the native peptide. Results from Ala scan studies of the sL1gamma peptide indicated that replacement of the residues (P3, G7, P8, P9 or N10) resulted in a remarkable drop in the activity, whereas replacement of residues K2, P4 or K6 by Ala resulted in enhancement of the antiplatelet activity by at least 10-fold. To examine the activity of multimeric L1gamma, several multimeric peptides were synthesized using the multiple-antigen peptide system assembled on a branched lysine core and their antiplatelet activity was evaluated in vitro. The largest multimeric peptides showed a 1,000-fold increase in antiplatelet activity.
Journal of Peptide Science, 2004
Journal of Molecular Biology, 2000
Multidimensional, homo- and heteronuclear magnetic resonance spectroscopy combined with dynamical... more Multidimensional, homo- and heteronuclear magnetic resonance spectroscopy combined with dynamical annealing has been used to determine the structure of a 94 residue module (X2 1) of the scaffolding protein CipC from the anaerobic bacterium Clostridium cellulolyticum. An experimental data set comprising 1647 nuclear Overhauser effect-derived restraints, 105 hydrogen bond restraints and 66 phi torsion angle restraints was used to calculate 20 converging final solutions. The calculated structures have an average rmsd about the mean structure of 0.55(+/-0.11) A for backbone atoms and 1.40(+/-0.11) A for all heavy atoms when fitted over the secondary structural elements. The X2 1 module has an immunoglobulin-like fold with two beta-sheets packed against each other. One sheet contains three strands, the second contains four strands. An additional strand is intercalated between the beta-sandwich, as well as two turns of a 3(.10) helix. X2 1 has a surprising conformational stability and may act as a conformational linker and solubility enhancer within the scaffolding protein. The fold of X2 1 is very similar to that of telokin, titin Ig domain, hemolin D2 domain, twitchin immunoglobulin domain and the first four domains of the IgSF portion of transmembrane cell adhesion molecule. As a consequence, the X2 1 module is the first prokaryotic member assigned to the I set of the immunoglobulin superfamily even though no sequence similarity with any member of this superfamily could be detected.
Journal of Medicinal Chemistry, 2012
Journal of Biological Chemistry, 2000
Biochemistry, 2001
Ptu1 is a toxin from the assassin bug Peirates turpis which has been demonstrated to bind reversi... more Ptu1 is a toxin from the assassin bug Peirates turpis which has been demonstrated to bind reversibly the N-type calcium channels and to have lower affinity than the omega-conotoxin MVIIA. We have determined the solution structure of Ptu1 by use of conventional two-dimensional NMR techniques followed by distance-geometry and molecular dynamics. The calculated structure of Ptu1 belongs to the inhibitory cystin knot structural family (ICK) that consists of a compact disulfide-bonded core from which four loops emerge. Analysis of the 25 converged solutions indicates that the molecular structure of Ptu1 contains a 2-stranded antiparallel beta-sheet (residues 24-27 and 31-34) as the only secondary structure. The loop 2 that has been described to be critical for the binding of the toxin on the channel is similar in Ptu1 and MVIIA. In this loop, the critical residue, Tyr13, in MVIIA is retrieved in Ptu1 as Phe13, but the presence of an acidic residue (Asp16) in Ptu1 could disturb the binding of Ptu1 on the channel and could explain the lower affinity of Ptu1 toward the N-type calcium channel compared to the one of MVIIA. Analysis of the electrostatic charge's repartition gives some insights about the importance of the basic residues, which could interact with acidic residues of the channel and then provide a stabilization of the toxin on the channel.
European Journal of Biochemistry
A group of ubiquitous small proteins (average 13 kDa) has been isolated from several sensory orga... more A group of ubiquitous small proteins (average 13 kDa) has been isolated from several sensory organs of a wide range of insect species. They are believed to be involved in chemical communication and perception (olfaction or taste) and have therefore been called chemo-sensory proteins (CSPs). Several CSPs have been identified in the antennae and proboscis of the moth Mamestra brassicae. We have expressed one of the antennal proteins (CSPMbraA6) in large quantities as a soluble recombinant protein in Escherichia coli periplasm. This 112-residue protein is a highly soluble monomer of 13 072 Da with a pI of 5.5. NMR data (1H and 15N) indicate that CSPMbraA6 is well folded and contains seven alpha helices (59 amino acids) and two short extended structures (12 amino acids) from positions 5 to 10 and from 107 to 112. Thirty-seven amino acids are involved in beta turns and coiled segments and four amino acids are not assigned in the NMR spectra (the N-terminus and the residue 52 in the loop ...
Journal of Biomolecular NMR
Staphylococcus aureus produces peptide toxins that it uses to respond to environmental cues. We p... more Staphylococcus aureus produces peptide toxins that it uses to respond to environmental cues. We previously characterized PepA1, a peptide toxin from S. aureus, that induces lytic cell death of both bacterial and host cells. That led us to suggest that PepA1 has an antibacterial activity. Here, we demonstrate that exogenously provided PepA1 has activity against both Gram-positive and Gram-negative bacteria. We also see that PepA1 is significantly hemolytic, thus limiting its use as an antibacterial agent. To overcome these limitations, we converted PepA1 into nonhemolytic derivatives. Our most promising derivative is a cyclic heptapseudopeptide with inconsequential toxicity to human cells, enhanced stability in human sera, and sharp antibacterial activity. Mechanistically, linear and helical PepA1 derivatives form pores at the bacterial and erythrocyte surfaces, while the cyclic peptide induces bacterial envelope reorganization, with insignificant action on the erythrocytes. Our work...
The viral broad spectrum chemokine vCCL2 binds to the chemokine receptors CXCR4 and CCR5 and inhi... more The viral broad spectrum chemokine vCCL2 binds to the chemokine receptors CXCR4 and CCR5 and inhibits HIV-1 entry protecting host cells against infection [1]. Peptide derived from vCCL2 N-terminus (vCCL2 1-21) displays modest CXCR4 and CXCR7 binding affinity and antiviral properties compared to the parental chemokine but mutations within its CC motif has been shown to enhance its antiviral properties, for review see [2]. In this study, we exploited these observations to develop highly potent and selective CXCR4 antagonists. The aim of the current study was to develop a new class of short and selective CXCR4 inhibitors inspired by the binding mode of natural chemokines (Mimokines). The N-terminus of vCCL2 (vCCL2 (1-21)), a viral chemokine displaying antagonist properties on CXCR4, was used as scaffold to introduce controlled randomizations and to create phage library of peptide variants. A Mimokine phage display library, in which C 11 C 12 amino acids within the N-terminus vCCL2 (1-2...
The Journal of biological chemistry, Jan 21, 2001
Polysaccharide-degrading enzymes are generally modular proteins that contain non-catalytic carboh... more Polysaccharide-degrading enzymes are generally modular proteins that contain non-catalytic carbohydrate-binding modules (CBMs), which potentiate the activity of the catalytic module. CBMs have been grouped into sequence-based families, and three-dimensional structural data are available for half of these families. Clostridium thermocellum xylanase 11A is a modular enzyme that contains a CBM from family 6 (CBM6), for which no structural data are available. We have determined the crystal structure of this module to a resolution of 2.1 A. The protein is a beta-sandwich that contains two potential ligand-binding clefts designated cleft A and B. The CBM interacts primarily with xylan, and NMR spectroscopy coupled with site-directed mutagenesis identified cleft A, containing Trp-92, Tyr-34, and Asn-120, as the ligand-binding site. The overall fold of CBM6 is similar to proteins in CBM families 4 and 22, although surprisingly the ligand-binding site in CBM4 and CBM22 is equivalent to cleft...
Chemistry & Biology, 2015
European Journal of Biochemistry, 2001
Peptides, 2004
Alpha scorpion toxins bind to receptor site 3 on voltage-dependent sodium channels and inhibit th... more Alpha scorpion toxins bind to receptor site 3 on voltage-dependent sodium channels and inhibit their inactivation. The α-scorpion toxin BotIII is the most toxic protein of Buthus occitanus tunetanus. Its sequence differs only by three amino acid residues from that of AahII, the most active α-toxin. Due to their high affinity and selectivity for mammalian sodium channels, BotIII and AahII
European Journal of Biochemistry, 2003
Proteins: Structure, Function, and Genetics, 2000
Proteins: Structure, Function, and Bioinformatics, 2005
Pathophysiology of Haemostasis and Thrombosis, 2001
Lebetins from Macrovipera lebetina snake venom constitute a new class of inhibitors of platelet a... more Lebetins from Macrovipera lebetina snake venom constitute a new class of inhibitors of platelet aggregation. There are two groups of peptides: lebetin 1 (L1; 11- to 13-mer) and lebetin 2 (L2; 37- to 38-mer). The short lebetins are identical to the N-terminal segments of the longer ones. They inhibit platelet aggregation induced by various agonists (e.g. thrombin, PAF-acether or collagen). The shortest lebetin (11-mer) shows potent inhibition of rabbit (IC(50) = 7 nM) and human (IC(50) = 5 nM) platelets. They prevent collagen-induced thrombocytopenia in rats. N- and C-terminal-truncated synthetic L1gamma (sL1gamma; 11-mer) is less active in inhibiting platelet aggregation than the native peptide. Results from Ala scan studies of the sL1gamma peptide indicated that replacement of the residues (P3, G7, P8, P9 or N10) resulted in a remarkable drop in the activity, whereas replacement of residues K2, P4 or K6 by Ala resulted in enhancement of the antiplatelet activity by at least 10-fold. To examine the activity of multimeric L1gamma, several multimeric peptides were synthesized using the multiple-antigen peptide system assembled on a branched lysine core and their antiplatelet activity was evaluated in vitro. The largest multimeric peptides showed a 1,000-fold increase in antiplatelet activity.
Journal of Peptide Science, 2004
Journal of Molecular Biology, 2000
Multidimensional, homo- and heteronuclear magnetic resonance spectroscopy combined with dynamical... more Multidimensional, homo- and heteronuclear magnetic resonance spectroscopy combined with dynamical annealing has been used to determine the structure of a 94 residue module (X2 1) of the scaffolding protein CipC from the anaerobic bacterium Clostridium cellulolyticum. An experimental data set comprising 1647 nuclear Overhauser effect-derived restraints, 105 hydrogen bond restraints and 66 phi torsion angle restraints was used to calculate 20 converging final solutions. The calculated structures have an average rmsd about the mean structure of 0.55(+/-0.11) A for backbone atoms and 1.40(+/-0.11) A for all heavy atoms when fitted over the secondary structural elements. The X2 1 module has an immunoglobulin-like fold with two beta-sheets packed against each other. One sheet contains three strands, the second contains four strands. An additional strand is intercalated between the beta-sandwich, as well as two turns of a 3(.10) helix. X2 1 has a surprising conformational stability and may act as a conformational linker and solubility enhancer within the scaffolding protein. The fold of X2 1 is very similar to that of telokin, titin Ig domain, hemolin D2 domain, twitchin immunoglobulin domain and the first four domains of the IgSF portion of transmembrane cell adhesion molecule. As a consequence, the X2 1 module is the first prokaryotic member assigned to the I set of the immunoglobulin superfamily even though no sequence similarity with any member of this superfamily could be detected.
Journal of Medicinal Chemistry, 2012
Journal of Biological Chemistry, 2000