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See detailPeptide G, containing the binding site of the 67-kDa laminin receptor, increases and stabilizes laminin binding to cancer cells.
Magnifico, A.; Tagliabue, E.; Buto, S. et al

in Journal of Biological Chemistry (1996), 271(49), 31179-84

We investigated the effect of peptide G, a synthetic peptide derived from the sequence of the 37-kDa laminin receptor precursor, on the interaction of laminin in two tumor cell lines one of which produces ... [more ▼]

We investigated the effect of peptide G, a synthetic peptide derived from the sequence of the 37-kDa laminin receptor precursor, on the interaction of laminin in two tumor cell lines one of which produces laminin and one of which does not. Addition of peptide G to the culture medium induced a significant increase in the amount of endogenous laminin detectable on the cell membrane of both cell lines. Moreover, pretreatment of exogenous laminin with peptide G dramatically increased laminin binding on both cell lines. Kinetics analysis of membrane-bound labeled laminin revealed a 3-fold decrease in the kd of peptide G-treated laminin compared with untreated or unrelated or scrambled peptide-treated laminin. Moreover, the affinity constant of peptide G-treated laminin increased 2-fold, with a doubling of the number of laminin binding sites, as determined by Scatchard analysis. Expression of the VLA6 integrin receptor on the cell membrane increased after incubation with peptide G-treated laminin. However, the lower binding inhibition of peptide G-treated laminin after anti-VLA6 antibody or cation chelation treatment indicates that membrane molecules in addition to integrin receptors are involved in the recognition of peptide G-modified laminin. These "new" laminin-binding proteins also mediated cell adhesion to laminin, the first step in tumor invasion. Together, the data suggest that peptide G increases and stabilizes laminin binding on tumor cells, involving surface receptors that normally do not take part in this interaction. This might explain the abundant clinical and experimental data suggesting a key role for the 67-kDa laminin receptor in the interaction between cancer cells and the basement membrane glycoprotein laminin during tumor invasion and metastasis. [less ▲]

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See detailPeptide hormones: from the transcription of the gene to the final product--a biochemical view
Martial, Joseph ULg

in Hormone Research (1989), 32(1-3), 9-12

This very short review aims at analyzing the current biochemical view of the molecular steps involved in the peptide hormone synthesis, going from the gene to the final active peptide.

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See detailPeptide inhibitors of Streptomyces DD-carboxypeptidases
Nieto, Manuel; Perkins, Harnold R.; Leyh-Bouille, Mélina et al

in Biochemical Journal (1973), 131(1), 163-171

1. Peptides that inhibit the dd-carboxypeptidases from Streptomyces strains albus G and R61 were synthesized. They are close analogues of the substrates of these enzymes. The enzymes from albus G and R61 ... [more ▼]

1. Peptides that inhibit the dd-carboxypeptidases from Streptomyces strains albus G and R61 were synthesized. They are close analogues of the substrates of these enzymes. The enzymes from albus G and R61 strains are in general inhibited by the same peptides, but the enzyme from strain R39 differs considerably. 2. The two C-terminal residues of the peptide substrates and inhibitors appear to be mainly responsible for the initial binding of the substrate to the enzymes from albus G and R61 strains. The side chain in the third residue from the C-terminus seems critical in inducing catalytic activity. 3. Experimental evidence is presented suggesting that the amide bond linking the two C-terminal residues has a cis configuration when bound to the enzymes from strains albus G and R61. 4. The peptide inhibitors are not antibiotics against the same micro-organisms. [less ▲]

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See detailA peptide mimicking the C-terminal part of the reactive center loop induces the transition to the latent form of Plasminogen Activator Inhibitor Type-1
D'Amico, Salvino ULg; Martial, Joseph ULg; Struman, Ingrid ULg

in FEBS Letters (2012), 586

Plasminogen Activator Inhibitor-1 (PAI-1) is the primary inhibitor of plasminogen activators (uPA and tPA) and thus plays a central role in fibrinolysis. The spontaneous insertion of its Reactive Centre ... [more ▼]

Plasminogen Activator Inhibitor-1 (PAI-1) is the primary inhibitor of plasminogen activators (uPA and tPA) and thus plays a central role in fibrinolysis. The spontaneous insertion of its Reactive Centre Loop (RCL) into beta-sheet A is responsible for its irreversible conversion into the inactive latent form. In this study, we used two peptides mimicking residues P14-P9 and P8-P3 of the RCL so as to understand this dynamic process. We show that both peptides inhibit the formation of PAI 1/uPA and PAI-1/tPA complexes via two different mechanisms. Targeting the N-terminal part of the loop induces the cleavage of PAI-1 by the proteases uPA/tPA while targeting its C-terminal part greatly favors the irreversible formation of latent PAI-1. [less ▲]

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See detailThe peptide N alpha-(L-alanyl-D-isoglutaminyl)-N epsilon-(D-isoasparaginyl)-L-lysyl-D-alanine and the disaccharide N-acetylglucosaminyl-beta-1,4-N-acetylmuramic acid in cell wall peptidoglycan of Streptococcus faecalis strain ATCC 9790
Ghuysen, Jean-Marie ULg; Bricas, E.; Leyh-Bouille, Martine et al

in Biochemistry (1967), 6(8), 2607-2619

A major portion of the cell wall peptidoglycan in Streptococcus faecalis is composed of the disaccharide tetrapeptide β-1,4-N-acetylglucosaminyl-N-acetylmuramyl-Nα-(L-alanyl-D-isoglutaminyl)-L-lysyl-D ... [more ▼]

A major portion of the cell wall peptidoglycan in Streptococcus faecalis is composed of the disaccharide tetrapeptide β-1,4-N-acetylglucosaminyl-N-acetylmuramyl-Nα-(L-alanyl-D-isoglutaminyl)-L-lysyl-D-alanine. The tetrapeptides are cross-linked through single D-isoasparaginyl residues extending from the C-terminal D-alanine of one tetrapeptide unit to the Nє-terminal L-lysine of another. It is the first time that the occurrence of an isoasparaginyl residue in a natural product has been described. The Streptomyces SA en-dopeptidase cleaves D-alanyl-D-isoasparaginyl linkages and is thus the first enzyme known to hydrolyze D-D peptide bonds. Treatment of the disaccharide Nα-( L-alanyl-D-isoglutaminyl)-N є-(D-isoasparaginyl)- L-lysil-D-alanine with 10 equiv of NaOH at 37° for 1 hr results in deamidation of the isoasparaginyl residue together with migration of the aspartyl-lysine peptide bond giving rise to a mixture of Nє-(β-aspartyl)- and N є-(α-aspartyl)lysyl peptides. Under the same alkaline treatment, the N-acetylmuramyl residue undergoes a lactyl elimination which results in the production of acyl peptides and a Morgan-Elson prochromogenic compound, without hydrolysis of the glycosidic linkage. This conversion, interpreted to be the result of a β elimination, also occurs in the other disaccharide peptide monomers previously isolated from Staphylococcus aureus, Micrococcus roseus, and Streptococcus pyogenes. [less ▲]

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See detailPEPTIDE-LOADED LIPOSOMES AGAINST BREAST CANCER: EFFECTIVE PENETRATION IN CELLS OF LONG CIRCULATING pH-SENSITIVE VESICLES
Ducat, Emilie ULg; Deprez, Julie ULg; Peulen, Olivier ULg et al

Poster (2010, October)

Purpose: Print3G, a peptidic antagonist of oncoprotein involved in breast cancer, could reduce the angiogenic development of breast tumors. The necessity of intravenous administration of Print3G led to ... [more ▼]

Purpose: Print3G, a peptidic antagonist of oncoprotein involved in breast cancer, could reduce the angiogenic development of breast tumors. The necessity of intravenous administration of Print3G led to the development of liposomes as drug carriers, combining the protective properties of PEG with the transfection properties of pH-sensitive lipids. The purpose of this work is to compare pegylated pH-sensitive liposomes with a classical formulation of long-circulating liposomes in terms of cellular uptake. Methods: Classical liposomes (SPC:CHOL:mPEG-750-DSPE (47:47:6 mol/mol)) and pH-sensitive liposomes (DOPE:CHEMS:CHOL: mPEG750-DSPE (43:21:30:6 mol/mol)) were compared in terms of size, charge, stability, pH-sensitivity and toxicity by inhibition of cell proliferation. Finally, confocal microscopy was used to study the cellular uptake of liposomes by three cell lines (Hs578t, WI-26 and MDA-MB-231), using 25-nitrobenzoxydiazol-cholesterol as a fluorescent marker of the vesicular membrane and rhodamine in the inner cavity of liposomes. Results: Sizes of 162.8 ± 4.6 nm and zeta potential of -9.3 ± 1.2 mV were obtained for standard liposomes (n=3) while the obtained values for pH-sensitive liposomes (n=3) were respectively of 184.8 ± 3.2 nm and -19.5 ± 2.6 mV. The two formulations were comparable in terms of shape and stability. Concerning the pH-sensitivity study, a significantly higher leakage of the encapsulated material was observed at pH 5 for pH-sensitive liposomes. Confocal pictures obtained with these vesicles on the three cell lines allowed us to visualize the colocalized red and green color with a higher concentration near the nucleus. Conclusion: Long circulating pH-sensitive liposomes are promising drug delivery systems in terms of cellular uptake. Experiments will be performed with biotinylated Print3G to assess its cellular distribution. Moreover, the accumulation of this formulation in breast tumor will be evaluated by in vivo studies. [less ▲]

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See detailPeptides As Drugs: Myth Or Reality?
Decaffmeyer, Marc ULg; Thomas, Annick ULg; Brasseur, Robert ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2008), 12(1),

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See detailPeptides entrapped in biodegradable PLGA microparticles accelerate tissue repair at gastric ulcer treatment in rats
Markvicheva, E; Stashevskaya, K; Prudchenko, I et al

Conference (2007, September 09)

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See detailPeptides in membranes: tipping the balance of membrane stability.
Brasseur, Robert ULg; Pillot, T.; Lins, Laurence ULg et al

in Trends in biochemical sciences (1997), 22(5), 167-71

This review describes a class of peptides that associate with lipids in membranes and are commonly known as 'oblique-orientated peptides'. Owing to an asymmetric distribution of hydrophobic residues along ... [more ▼]

This review describes a class of peptides that associate with lipids in membranes and are commonly known as 'oblique-orientated peptides'. Owing to an asymmetric distribution of hydrophobic residues along the axis of the alpha-helix, such peptides can destabilize membranes or lipid cores, thereby facilitating such cellular processes as vesicular fusion or protein transport across subcellular compartments, as well as remodelling of lipid cores. [less ▲]

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See detailLes peptides natriurétiques: le point de vue du biologiste
LE GOFF, Caroline ULg

Conference (2015, February 26)

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See detailPeptides neurohypophysaires et dépression unipolaire: quel avenir?.
Scantamburlo, Gabrielle ULg; Pitchot, William ULg; Ansseau, Marc ULg et al

in Revue Médicale de Liège (2008), 63

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See detailPeptides obliques: Etat des lieux
Lins, Laurence ULg

Conference (2010, November 17)

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See detailThe peptidoglycan crosslinking enzyme system in Streptomyces R61, K15 and rimosus. Immunological studies
Nguyen-Distèche, Martine ULg; Frère, Jean-Marie ULg; Dusart, Jean et al

in European Journal of Biochemistry (1977), 81(1), 29-32

The exocellular DD-carboxypeptidases from Streptomyces R61, K 15, the lysozyme-releasable DD-carboxypeptidases from Streptomyces R61, K15 and rimosus, and the membrane-bound DD-carboxypeptidase of ... [more ▼]

The exocellular DD-carboxypeptidases from Streptomyces R61, K 15, the lysozyme-releasable DD-carboxypeptidases from Streptomyces R61, K15 and rimosus, and the membrane-bound DD-carboxypeptidase of Streptomyces K15 are immunologically related to each other. [less ▲]

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See detailThe peptidoglycan crosslinking enzyme system in Streptomyces strains R61, K15 and rimosus : Kinetic Coefficients Involved in the Interactions of the Membrane-Bound Transpeptidase with Peptide Substrates and β-Lactam Antibiotics
Dusart, Jean; Leyh-Bouille, Mélina; Ghuysen, Jean-Marie ULg

in European Journal of Biochemistry (1977), 81(1), 33-44

The transpeptidation reaction performed by the membranes of Streptomyces strain R61 fits the general rate equation for an enzyme-catalysed bimolecular reaction. The same membranes (E) interact with beta ... [more ▼]

The transpeptidation reaction performed by the membranes of Streptomyces strain R61 fits the general rate equation for an enzyme-catalysed bimolecular reaction. The same membranes (E) interact with beta-lactams (I) to form inactive penicillin-enzyme-membrane complexes (EI) of rather high stability, which subsequently break down (E + I leads to EI leads to E + degradation products). The enzyme is regenerated and the antibiotic is released in the form of an inactive metabolite. With benzylpenicillin, the degradation product is benzylpenicilloic acid. The reaction is heat-labile. The first step of the reaction (E + I leads to EI) is characterized by a second-order rate constant (kformation in M-1 s-1) and the second step (EI leads to E + degradation products) by a first-order rate constant (kbreakdown in s-1). The effects in vitro of various beta-lactams on the membrane-bound transpeptidase, as expressed by the relevant kformation and kbreakdown values, parallel the effects in vivo of the same antibiotics as expressed by their ability to prevent the germination and growth of conidiospores. The kinetic parameters of the transpeptidase that was solubilized with N-cetyl-N,N,N-trimethylammonium bromide with respect to its interaction with both peptide substrates and beta-lactam antibiotics are quantitatively different from those of the membrane-bound enzyme. Moreover, the solubilized enzyme fragments benzylpenicillin with formation of phenylacetylglycine, a reaction which is similar to that catalysed by the exocellular R61 enzyme. The membranes of Streptomyces strains rimosus and K15 possess an active 'classic' penicillinase. They were not studied but the kinetic coefficients of the corresponding solubilized transpeptidases were determined and compared with those of the solubilized enzyme from strain R61. [less ▲]

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See detailThe peptidoglycan crosslinking enzyme system in Streptomyces strains R61, K15 and rimosus. Exocellular, lysozyme-releasable and membrane-bound enzymes.
Leyh-Bouille, Mélina; Dusart, Jean; Nguyen Van, Martine ULg et al

in European Journal of Biochemistry (1977), 81(1), 19-28

The DD-carboxypeptidase (I)-transpeptidase (II) system in Streptomyces strain K15 consists of: (1) a membrane-bound II capable of performing low I activity; and (2) a set of I: (a) membrane-bound, (b ... [more ▼]

The DD-carboxypeptidase (I)-transpeptidase (II) system in Streptomyces strain K15 consists of: (1) a membrane-bound II capable of performing low I activity; and (2) a set of I: (a) membrane-bound, (b) lysozyme-releasable, and (c) exocellular, having low II activities in aq. media and at low acceptor concns. The I are related to each other and may belong to the same pathway leading to enzyme excretion. A similar system occurs in Streptomyces strain R61 except that the membrane-bound I activity is low when compared with the membrane-bound II activity. In S. rimosus, the system consists almost exclusively of the membrane-bound II and the levels of membrane-bound, lysozyme-releasable, and exocellular I are very low. [on SciFinder(R)] [less ▲]

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See detailA peptidoglycan fragment triggers beta-lactam resistance in Bacillus licheniformis.
Amoroso, Ana Maria ULg; Boudet, Julien; Berzigotti, Stephanie et al

in PLoS Pathogens (2012), 8(3), 1002571

To resist to beta-lactam antibiotics Eubacteria either constitutively synthesize a beta-lactamase or a low affinity penicillin-binding protein target, or induce its synthesis in response to the presence ... [more ▼]

To resist to beta-lactam antibiotics Eubacteria either constitutively synthesize a beta-lactamase or a low affinity penicillin-binding protein target, or induce its synthesis in response to the presence of antibiotic outside the cell. In Bacillus licheniformis and Staphylococcus aureus, a membrane-bound penicillin receptor (BlaR/MecR) detects the presence of beta-lactam and launches a cytoplasmic signal leading to the inactivation of BlaI/MecI repressor, and the synthesis of a beta-lactamase or a low affinity target. We identified a dipeptide, resulting from the peptidoglycan turnover and present in bacterial cytoplasm, which is able to directly bind to the BlaI/MecI repressor and to destabilize the BlaI/MecI-DNA complex. We propose a general model, in which the acylation of BlaR/MecR receptor and the cellular stress induced by the antibiotic, are both necessary to generate a cell wall-derived coactivator responsible for the expression of an inducible beta-lactam-resistance factor. The new model proposed confirms and emphasizes the role of peptidoglycan degradation fragments in bacterial cell regulation. [less ▲]

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See detailPeptidoglycan Glycosyltransferase Inhibition: New Perspectives for An Old Target.
Terrak, Mohammed ULg

in Anti-Infective Agents in Medicinal Chemistry (2008)

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See detailPeptidoglycan glycosyltransferase substrate mimics as templates for the design of new antibacterial drugs.
Derouaux, Adeline ULg; Sauvage, Eric ULg; Terrak, Mohammed ULg

in Frontiers in immunology (2013), 4

Peptidoglycan (PG) is an essential net-like macromolecule that surrounds bacteria, gives them their shape, and protects them against their own high osmotic pressure. PG synthesis inhibition leads to ... [more ▼]

Peptidoglycan (PG) is an essential net-like macromolecule that surrounds bacteria, gives them their shape, and protects them against their own high osmotic pressure. PG synthesis inhibition leads to bacterial cell lysis, making it an important target for many antibiotics. The final two reactions in PG synthesis are performed by penicillin-binding proteins (PBPs). Their glycosyltransferase (GT) activity uses the lipid II precursor to synthesize glycan chains and their transpeptidase (TP) activity catalyzes the cross-linking of two glycan chains via the peptide side chains. Inhibition of either of these two reactions leads to bacterial cell death. beta-lactam antibiotics target the transpeptidation reaction while antibiotic therapy based on inhibition of the GTs remains to be developed. Ongoing research is trying to fill this gap by studying the interactions of GTs with inhibitors and substrate mimics and utilizing the latter as templates for the design of new antibiotics. In this review we present an updated overview on the GTs and describe the structure-activity relationship of recently developed synthetic ligands. [less ▲]

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