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See detailRagged N-Termini and Other Variants of Class a Beta-Lactamases Analysed by Chromatofocusing
Matagne, André ULg; Joris, Bernard ULg; Van Beeumen, J. et al

in Biochemical Journal (1991), 273(273), 503-10

Four beta-lactamases excreted by Gram-positive bacteria exhibited microheterogeneity when analysed by chromatofocusing or ion-exchange chromatography. Ragged N-termini were in part responsible for the ... [more ▼]

Four beta-lactamases excreted by Gram-positive bacteria exhibited microheterogeneity when analysed by chromatofocusing or ion-exchange chromatography. Ragged N-termini were in part responsible for the charge variants, but deamidation of an asparagine residue was also involved, at least for the Bacillus licheniformis enzyme. The activity of a contaminating proteinase could also be demonstrated in the case of Actinomadura R39 beta-lactamase. With that enzyme, proteolysis resulted in partial inactivation, but the inactivated fragments were easily separated from the active forms. With these, as with the other enzymes, the kinetic parameters of the major variants were identical with those of the mixture within the limits of experimental error, so that the catalytic properties of these enzymes can be determined with the 'heterogeneous' preparations. [less ▲]

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See detailMechanism of action of β-lactamases and DD-peptidases
Frère, Jean-Marie ULg; Joris, Bernard ULg; Jacob, Françoise et al

in Pandit, U.K.; Alderweireldt, F.C. (Eds.) Bioorganic Chemistry in Healthcare and Technology (1991)

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See detailSequence analysis of the ARG7 gene of Schizosaccharomyces pombe coding for argininosuccinate lyase. Expression of the gene in Saccharomyces cerevisiae.
Loppes, Roland ULg; Michels, R; Decroupette, I et al

in Current Genetics (1991), 19(4), 255-60

The complete nucleotide sequence of the ARG7 gene, coding for argininosuccinate lyase (EC 4.3.2.1), in the fission yeast (Schizosaccharomyces pombe) has been determined. It consists of an open reading ... [more ▼]

The complete nucleotide sequence of the ARG7 gene, coding for argininosuccinate lyase (EC 4.3.2.1), in the fission yeast (Schizosaccharomyces pombe) has been determined. It consists of an open reading frame of 461 codons. The deduced protein has a molecular weight of 51,200 Da. The gene is devoid of introns which is confirmed by the fact that it is expressed in Escherichia coli after spontaneous insertion of a bacterial sequence probably bearing a prokaryotic promoter. A perfect "TATA" box is found at -72 and the major transcription initiation site in Saccharomyces cerevisiae is located at -11 as shown by primer extension experiments. Comparison of the S. pombe lyase with related proteins from other organisms reveals an important degree of conservation except in the carboxyterminal part of the polypeptide. Additionally, a deletion removing 66 amino acids of the carboxy terminus yields an enzyme exhibiting some biological activity. A unique 1,500 b transcript was found in S. cerevisiae when the intact gene was present, but the deleted version of the gene gave rise to at least three transcripts of 1,800, 2,800 and 3,900 b. [less ▲]

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See detailCloning and nucleotide sequencing of the gene encoding the beta-lactamase from Citrobacter diversus
Perilli, Mariagrazia; Franceschini, Nicola; Segatore, Bernardetta et al

in FEMS Microbiology Letters (1991), 83

The gene coding for the class A beta-lactamase of Citrobacter diversus has been cloned and sequenced. It contains the information for a 294-amino-acid precursor protein, including a 27-residue N-terminal ... [more ▼]

The gene coding for the class A beta-lactamase of Citrobacter diversus has been cloned and sequenced. It contains the information for a 294-amino-acid precursor protein, including a 27-residue N-terminal signal peptide. The deduced sequence of the N-terminal portion of the mature protein is in excellent agreement with that determined by microsequencing of the protein and readily explains the pI differences observed between the naturally occurring forms I and II of the enzyme. The sequence of the mature protein exhibits a very high degree of similarity with that of the Klebsiella oxytoca class A beta-lactamase [less ▲]

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See detailTHE MUTATION LYS234HIS YIELDS A CLASS-A BETA-LACTAMASE WITH A NOVEL PH-DEPENDENCE
BRANNIGAN, J.; Matagne, André ULg; Jacob, Françoise et al

in Biochemical Journal (1991), 278(Part 3), 673-678

The lysine-234 residue is highly conserved in beta-lactamases and in nearly all active-site-serine penicillin-recognizing enzymes. Its replacement by a histidine residue in the Streptomyces albus G class ... [more ▼]

The lysine-234 residue is highly conserved in beta-lactamases and in nearly all active-site-serine penicillin-recognizing enzymes. Its replacement by a histidine residue in the Streptomyces albus G class A beta-lactamase yielded an enzyme the pH-dependence of which was characterized by the appearance of a novel pK, which could be attributed to the newly introduced residue. At low pH, the k(cat.) value for benzylpenicillin was as high as 50 % of that of the wild-type enzyme, demonstrating that an efficient active site was maintained. Both k(cat.) and k(cat.)/K(m) dramatically decreased above pH 6 but the decrease in k(cat.)/K(m) could not be attributed to larger K(m) values. Thus a positive charge on the side chain of residue 234 appears to be more essential for transition-state stabilization than for initial recognition of the substrate ground state. [less ▲]

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See detailDiversity of the Mechanisms of Resistance to Beta-Lactam Antibiotics
Frère, Jean-Marie ULg; Joris, Bernard ULg; Granier, B. et al

in Research in Microbiology (1991), 142(6, Jul-Aug), 705-10

The sensitivity of a bacterium to beta-lactam antibiotics depends upon the interplay between 3 independent factors: the sensitivity of the essential penicillin-binding enzyme(s), the quantity and ... [more ▼]

The sensitivity of a bacterium to beta-lactam antibiotics depends upon the interplay between 3 independent factors: the sensitivity of the essential penicillin-binding enzyme(s), the quantity and properties of the beta-lactamase(s) and the diffusion barrier that the outer-membrane of Gram-negative bacteria can represent. Those three factors can be modified by mutations or by the horizontal transfer of genes or portions of genes. [less ▲]

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See detailRole of the Conserved Amino Acids of the 'Sdn' Loop (Ser130, Asp131 and Asn132) in a Class a Beta-Lactamase Studied by Site-Directed Mutagenesis
Jacob, Françoise; Joris, Bernard ULg; Lepage, Sophie et al

in Biochemical Journal (1990), 271(2), 399-406

Ser130, Asp131 and Asn132 ('SDN') are highly conserved residues in class A beta-lactamases forming one wall of the active-site cavity. All three residues of the SDN loop in Streptomyces albus G beta ... [more ▼]

Ser130, Asp131 and Asn132 ('SDN') are highly conserved residues in class A beta-lactamases forming one wall of the active-site cavity. All three residues of the SDN loop in Streptomyces albus G beta-lactamase were modified by site-directed mutagenesis. The mutant proteins were expressed in Streptomyces lividans, purified from culture supernatants and their kinetic parameters were determined for several substrates. Ser130 was substituted by Asn, Ala and Gly. The first modification yielded an almost totally inactive protein, whereas the smaller-side-chain mutants (A and G) retained some activity, but were less stable than the wild-type enzyme. Ser130 might thus be involved in maintaining the structure of the active-site cavity. Mutations of Asp131 into Glu and Gly proved to be highly detrimental to enzyme stability, reflecting significant structural perturbations. Mutation of Asn132 into Ala resulted in a dramatically decreased enzymic activity (more than 100-fold) especially toward cephalosporin substrates, kcat. being the most affected parameter, which would indicate a role of Asn132 in transition-state stabilization rather than in ground-state binding. Comparison of the N132A and the previously described N132S mutant enzymes underline the importance of an H-bond-forming residue at position 132 for the catalytic process. [less ▲]

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See detailEngineering a Novel β-Lactamase by a Single Point Mutation
Jacob, F.; Joris, Bernard ULg; Dideberg, O. et al

in Protein Engineering (1990), 4(1), 79-86

beta-Lactamases are widespread and efficient bacterial enzymes which play a major role in bacterial resistance to penicillins and cephalosporins. In order to elucidate the role of the residues lying in a ... [more ▼]

beta-Lactamases are widespread and efficient bacterial enzymes which play a major role in bacterial resistance to penicillins and cephalosporins. In order to elucidate the role of the residues lying in a conserved loop of the enzymatic cavity of the active-site serine Streptomyces albus G beta-lactamase, modified proteins were produced by oligo-directed mutagenesis. Mutation of Asn116, which lies on one side of the active site cavity pointing to the substrate-binding site, into a serine residue resulted in spectacular modifications of the specificity profile of the enzyme. That replacement yielded an enzyme with a nearly unchanged activity towards good penicillin substrates. In sharp contrast its efficiency in hydrolysing cephalosporins was drastically reduced, the best substrates suffering the largest decrease in the second-order rate constant for serine acylation. In fact that single mutation generated a truly new enzyme behaving exclusively as a penicillinase, a situation which is never encountered to the same degree in any of the numerous naturally occurring variants of class A beta-lactamases. [less ▲]

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See detailExpression in Escherichia Coli of the Carboxy Terminal Domain of the Blar Sensory-Transducer Protein of Bacillus Licheniformis as a Water-Soluble Mr 26,000 Penicillin-Binding Protein
Joris, Bernard ULg; Ledent, P.; Kobayashi, T. et al

in FEMS Microbiology Letters (1990), 58(1), 107-113

A cloning vector has been constructed which allows production and export by Escherichia coli of the Met346-Arg601 carboxy terminal domain of the 601 amino acid BLAR sensory-transducer involved in beta ... [more ▼]

A cloning vector has been constructed which allows production and export by Escherichia coli of the Met346-Arg601 carboxy terminal domain of the 601 amino acid BLAR sensory-transducer involved in beta-lactamase inducibility in Bacillus licheniformis. The polypeptide, referred to as BLAR-CTD, accumulates in the periplasm of E. coli in the form of a water-soluble, Mr 26,000 penicillin-binding protein. These data and homology searches suggest that BLAR has a membrane topology similar to that of other sensory-transducers involved in chemotaxis. [less ▲]

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See detailThe Life-Cycle Proteins Roda of Escherichia Coli and Spove of Bacillus Subtilis Have Very Similar Primary Structures
Joris, Bernard ULg; Dive, Georges ULg; Henriques, A. et al

in Molecular Microbiology (1990), 4(3), 513-517

Comparison of the predicted amino acid sequence of the cell-cycle RodA protein with the National Research Foundation protein sequence database shows that the 370-amino-acid RodA, a protein that is ... [more ▼]

Comparison of the predicted amino acid sequence of the cell-cycle RodA protein with the National Research Foundation protein sequence database shows that the 370-amino-acid RodA, a protein that is essential for wall elongation in Escherichia coli and maintenance of the rod shape of the cell, is highly analogous, in terms of primary structure, with the Bacillus subtilis SpoVE protein involved in stage V of sporulation. [less ▲]

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See detailIdentification of BlaR, the signal transducer for β-lactamase production in Bacillus licheniformis, as a penicillin-binding protein with strong homology to the OXA-2 β-lactamase (class D) of Salmonella typhimurium
Zhu, Ying-Fang; Curran, Ivan H. A.; Joris, Bernard ULg et al

in Journal of Bacteriology (1990), 172(2), 1137-1141

The blaR gene of Bacillus licheniformis encodes the signal transducer for induction of the class A beta-lactamase. The protein product, BlaR, has a hydrophilic carboxy region that binds beta-lactams and ... [more ▼]

The blaR gene of Bacillus licheniformis encodes the signal transducer for induction of the class A beta-lactamase. The protein product, BlaR, has a hydrophilic carboxy region that binds beta-lactams and shows high sequence homology to the class D beta-lactamases, particularly the OXA-2 beta-lactamase of Salmonella typhimurium. The BlaR-beta-lactam complex is stable and may provide the continuing stimulus needed for the prolonged production of the enzyme. [less ▲]

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See detailThe Diversity of the Catalytic Properties of Class a Beta-Lactamases
Matagne, André ULg; Misselyn-Bauduin, A. M.; Joris, Bernard ULg et al

in Biochemical Journal (1990), 265(1), 131-46

The catalytic properties of four class A beta-lactamases were studied with 24 different substrates. They exhibit a wide range of variation. Similarly, the amino acid sequences are also quite different ... [more ▼]

The catalytic properties of four class A beta-lactamases were studied with 24 different substrates. They exhibit a wide range of variation. Similarly, the amino acid sequences are also quite different. However, no relationships were found between the sequence similarities and the substrate profiles. Lags and bursts were observed with various compounds containing a large sterically hindered side chain. As a group, the enzymes could be distinguished from the class C beta-lactamases on the basis of the kappa cat. values for several substrates, particularly oxacillin, cloxacillin and carbenicillin. Surprisingly, that distinction was impossible with the kappa cat./Km values, which represent the rates of acylation of the active-site serine residue by the beta-lactam. For several cephalosporin substrates (e.g. cefuroxime and cefotaxime) class A enzymes consistently exhibited higher kappa cat. values than class C enzymes, thus belying the usual distinction between 'penicillinases' and 'cephalosporinases'. The problem of the repartition of class A beta-lactamases into sub-classes is discussed. [less ▲]

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See detailNucleotide sequences of the pbpX genes encoding the penicillin-binding proteins 2x from Streptococcus pneumoniae R6 and a cefotaxime-resistant mutant, C506
Laible, G.; Hakenbeck, R.; Sicard, M. A. et al

in Molecular Microbiology (1989), 3(10), 1337-1348

Development of penicillin resistance in Streptococcus pneumoniae is due to successive mutations in penicillin-binding proteins (PBPs) which reduce their affinity for beta-lactam antibiotics. PBP2x is one ... [more ▼]

Development of penicillin resistance in Streptococcus pneumoniae is due to successive mutations in penicillin-binding proteins (PBPs) which reduce their affinity for beta-lactam antibiotics. PBP2x is one of the high-Mr PBPs which appears to be altered both in resistant clinical isolates, and in cefotaxime-resistant laboratory mutants. In this study, we have sequenced a 2564 base-pair chromosomal fragment from the penicillin-sensitive S. pneumoniae strain R6, which contains the PBP2x gene. Within this fragment, a 2250 base-pair open reading frame was found which coded for a protein having an Mr of 82.35kD, a value which is in good agreement with the Mr of 80-85 kD measured by SDS-gel electrophoresis of the PBP2x protein itself. The N-terminal region resembled an unprocessed signal peptide and was followed by a hydrophobic sequence that may be responsible for membrane attachment of PBP2x. The corresponding nucleotide sequence of the PBP2x gene from C504, a cefotaxime-resistant laboratory mutant obtained after five selection steps, contained three nucleotide substitutions, causing three amino acid alterations within the beta-lactam binding domain of the PBP2x protein. Alterations affecting similar regions of Escherichia coli PBP3 and Neisseria gonorrhoeae PBP2 from beta-lactam-resistant strains are known. The penicillin-binding domain of PBP2x shows highest homology with these two PBPs and S. pneumoniae PBP2b. In contrast, the N-terminal extension of PBP2x has the highest homology with E. coli PBP2 and methicillin-resistant Staphylococcus aureus PBP2'. No significant homology was detected with PBP1a or PBP1b of Escherichia coli, or with the low-Mr PBPs. [less ▲]

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See detailQuantitative Relationship between Sensitivity to Beta-Lactam Antibiotics and Beta-Lactamase Production in Gram-Negative Bacteria--II. Non-Steady-State Treatment and Progress Curves
Frère, Jean-Marie ULg; Joris, Bernard ULg; Crine, Michel ULg et al

in Biochemical Pharmacology (1989), 38(9), 1427-33

A non-steady-state model is discussed for the study of the interplay between beta-lactamase activity and outer membrane permeability with slowly hydrolysed beta-lactams. The analysis shows: (1) that the ... [more ▼]

A non-steady-state model is discussed for the study of the interplay between beta-lactamase activity and outer membrane permeability with slowly hydrolysed beta-lactams. The analysis shows: (1) that the simple, steady-state model presented in the accompanying paper remains valid as long as kcat (i.e. k3 with chromosome-encoded class C beta-lactamases) is larger than 10(-3)/sec (generation time = 20 min or more); (2) that among the beta-lactam antibiotics studied here, the complete, non-steady-state model needs only be used in the case of aztreonam; (3) that the term "trapping" should be replaced by "formation of a covalent acyl-enzyme" and that such a phenomenon only contributes significantly to the resistance when penetration and hydrolysis are very slow and the periplasmic beta-lactamase concentration is very high. Aztreonam seems to be the only compound which fulfils the first two conditions. [less ▲]

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See detailThe Streptomyces K15 DD-peptidase/penicillin-binding protein. Active site and sequence of the N-terminal region.
Leyh-Bouille, Mélina; Vanbeeumen, Jozef; Renier-Pirlot, Suzanne et al

in Biochemical Journal (1989), 260(2), 601-604

The N-terminal region of the Streptomyces K15 DD-peptidase/penicillin-binding protein shows high homology with that of other penicillin-interactive proteins or domains. The active-site serine residue of ... [more ▼]

The N-terminal region of the Streptomyces K15 DD-peptidase/penicillin-binding protein shows high homology with that of other penicillin-interactive proteins or domains. The active-site serine residue of the conserved tetrad Ser-Xaa-Xaa-Lys occurs at position 35. There is no indication for the presence of a signal peptide or an N-terminal hydrophobic sequence, suggesting that the Streptomyces K15 enzyme is probably anchored to the membrane by a C-terminal peptide segment. [less ▲]

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See detailSequence and Comparative Analysis of Three Enterobacter Cloacae Ampc Beta-Lactamase Genes and Their Products
Galleni, Moreno ULg; Lindberg, F.; Normark, S. et al

in Biochemical Journal (1988), 250(3), 753-60

The sequences of three Enterobacter cloacae ampC beta-lactamase genes have been determined. The deduced amino acid sequences are very similar: out of a total of 361 residues, only eight positions were ... [more ▼]

The sequences of three Enterobacter cloacae ampC beta-lactamase genes have been determined. The deduced amino acid sequences are very similar: out of a total of 361 residues, only eight positions were found to be variable, and several mutations yielded residues with very similar properties. The kinetic properties of two of the enzymes were not significantly different. The three enzymes also exhibited a high degree of homology (greater than 70%) with the ampC beta-lactamases of Escherichia coli K12 and Citrobacter freundii, confirming the homogeneity of class-C beta-lactamases. [less ▲]

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See detailThe Active-Site-Serine Penicillin-Recognizing Enzymes as Members of the Streptomyces R61 Dd-Peptidase Family
Joris, Bernard ULg; Ghuysen, Jean-Marie ULg; Dive, Georges ULg et al

in Biochemical Journal (1988), 250(2), 313-324

Homology searches and amino acid alignments, using the Streptomyces R61 DD-peptidase/penicillin-binding protein as reference, have been applied to the beta-lactamases of classes A and C, the Oxa-2 beta ... [more ▼]

Homology searches and amino acid alignments, using the Streptomyces R61 DD-peptidase/penicillin-binding protein as reference, have been applied to the beta-lactamases of classes A and C, the Oxa-2 beta-lactamase (considered as the first known member of an additional class D), the low-Mr DD-peptidases/penicillin-binding proteins (protein no. 5 of Escherichia coli and Bacillus subtilis) and penicillin-binding domains of the high-Mr penicillin-binding proteins (PBP1A, PBP1B, PBP2 and PBP3 of E. coli). Though the evolutionary distance may vary considerably, all these penicillin-interactive proteins and domains appear to be members of a single superfamily of active-site-serine enzymes distinct from the classical trypsin or subtilisin families. The amino acid alignments reveal several conserved boxes that consist of strict identities or homologous amino acids. The significance of these boxes is highlighted by the known results of X-ray crystallography, chemical derivatization and site-directed-mutagenesis experiments. [less ▲]

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See detailStructure-Activity Relationships in the Beta-Lactam Family: An Impossible Dream
Frère, Jean-Marie ULg; Joris, Bernard ULg; Varetto, Louis ULg et al

in Biochemical Pharmacology (1988), 37(1), 125-32

The difficulty of establishing structure-activity relationships in the beta-lactam family of antibiotics stems from the fact that: (1) The targets in various bacteria exhibit widely different ... [more ▼]

The difficulty of establishing structure-activity relationships in the beta-lactam family of antibiotics stems from the fact that: (1) The targets in various bacteria exhibit widely different sensitivities. (2) Some bacteria produce beta-lactamases, enzymes capable of destroying the antibiotics. The rates of the reactions with the beta-lactamases and the target enzymes are not necessarily related. (3) In Gram-negative bacteria, the diffusion rate through the outer membrane varies independently from the two other factors. [less ▲]

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See detailPurification and Characterization of a β-lactam-Resistant Penicillin-Binding Protein from Enterococcus hirae (Streptococcus faecium)
Jacques, Philippe; El Kharroubi, Aboubaker; Joris, Bernard ULg et al

in Actor, Paul; Daneo-Moore, Lolita; Higgins, Michael L. (Eds.) et al Antibiotic Inhibition of Bacterial Cell Surface Assembly and Function (1988)

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See detailChromosome-encoded beta-lactamases of Citrobacter diversus. Interaction with beta-iodopenicillanate and labelling of the active site.
Amicosante, G; Oratore, A; Joris, Bernard ULg et al

in Biochemical Journal (1988), 254(3), 891-3

Both forms of the chromosome-encoded beta-lactamase of Citrobacter diversus react with beta-iodopenicillanate at a rate characteristic of class A beta-lactamases. The active site of form I was labelled ... [more ▼]

Both forms of the chromosome-encoded beta-lactamase of Citrobacter diversus react with beta-iodopenicillanate at a rate characteristic of class A beta-lactamases. The active site of form I was labelled with the same reagent. The sequence of the peptide obtained after trypsin hydrolysis is identical with that of a peptide obtained in a similar manner from the chromosome-encoded beta-lactamase of Klebsiella pneumoniae. [less ▲]

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