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See detailMutation de LH
Beckers, Albert ULg

Scientific conference (2007, June 30)

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See detailMutation de LH
Beckers, Albert ULg

Scientific conference (2007, May 26)

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See detailMutation des systèmes partisans et résultats électoraux : Proportion congrue et gouvernabilité
Verjans, Pierre ULg

in Matagne, Geoffroy; Beaufays, Jean (Eds.) La Belgique en mutation : Systèmes politiques et politiques publiques (1968-2008) (2009)

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See detailMutation douce de l'enseignant en concepteur-tuteur dans des activités d'apprentissage totalement à distance. Communication présentée au Colloque TICE Méditérannée, Nice
Vandeput, Etienne ULg; Denis, Brigitte ULg

in Actes du colloque TICE Méditérannée (en ligne) (2004, November 26)

Experts in education and communication technology cannot speak about distance learning without calling up the new roles it springs up and the new relationships it generates. Its detractors claim that ... [more ▼]

Experts in education and communication technology cannot speak about distance learning without calling up the new roles it springs up and the new relationships it generates. Its detractors claim that, under these new conditions, this kind of learning requires significant and expansive means unlike a more classical one. Instead of giving up in front of such disheartening elements, the authors have been trying to measure how far a simple distance learning system (i.e. with little human, hardware and software means) can be implemented. In that way, they have been creating a learning environment basically based on a mixture of individual and collaborative works. Owing to both this mixture and the organization structure, the students can reach the fixed learning goals. Through these processes, they try to isolate practices, learners or teaching staff should be inspired by. They should, in that way, evolve slightly from a classical context to the design of learning scripts including efficient tutoring in a distance context. The course described in this paper is called “Analysis of distance learning environments”. The public consists of adults having enrolled for a DES in Education and Training Technology. To conduct this experiment, the authors have been setting themselves some rules and constraints in order to derive a general process that might be applied to various situations. These rules and constraints are very close to the usual learner’s working constraints. Recommendations focus on practices including careful preparation, coordination techniques betweenteachers and learner’s initiation into reflexivity. [less ▲]

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See detailMutation du gène AIP dans les FIPA
Beckers, Albert ULg

Scientific conference (2006, December 02)

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See detailMutation in exon 5 of bovine prolactin gene is not associated with milk traits in Holstein bulls.
Parmentier, Isabelle; Gengler, Nicolas ULg; Laliberte, P. et al

in ASAS/ADSA Joint Meeting (2000, July)

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See detailMutation in exon 5 of bovine prolactin gene is not associated with milk traits in Holstein bulls.
Parmentier, Isabelle; Gengler, Nicolas ULg; Laliberte, P. et al

in Journal of Animal Science (2000), 78(Suppl 1),

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See detailA mutation in the GTPase domain of the large subunit rRNA is involved in the suppression of a -1T frameshift mutation affecting a mitochondrial gene in Chlamydomonas reinhardtii
Matagne, René-Fernand ULg; Baurain, Denis ULg

in Molecular Genetics & Genomics (2001), 266(1), 103-108

The dum19 mutation isolated in Chlamydomonas reinhardtii is due to the deletion of one T at codon 152 of the mitochondrial cox1 gene sequence. Phenotypically, the dum19 mutant is characterized by a lack ... [more ▼]

The dum19 mutation isolated in Chlamydomonas reinhardtii is due to the deletion of one T at codon 152 of the mitochondrial cox1 gene sequence. Phenotypically, the dum19 mutant is characterized by a lack of cytochrome c oxidase activity and is unable to grow under heterotrophic conditions. A spontaneous pseudo-revertant that grows slowly in the dark was isolated from the dum19 mutant strain. A genetic and molecular analysis allowed us to demonstrate that the revertant phenotype is the consequence of two additional mutations that together act as a frameshift suppressor: an m mutation affecting a mitochondrial gene other than cox1 and an n mutation affecting a nuclear gene. On its own the n mutation does not act as a suppressor, whereas the m mutation very slightly compensates for the effect of the -1T mutation. Sequencing analysis showed that the m mutation affects the GTPase-associated domain of the large subunit (LSU) ofmitochondrial rRNA. Surprisingly, two substitutions, A1090 to G and A1098 to C, were found in the LSU rRNA of the revertant, the latter one being already present in the dum19 mutant strain itself. The A1090 to G substitution is thus involved in the suppression of the frameshift mutation, but it is not clear whether the change at position 1098 is also required for the expression of the suppressed phenotype. To our knowledge, this is the first example of a mutation in the GTPase-associated domain acting as a suppressor of a frameshift mutation. [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 detailMutation of the iron-sulfur cluster assembly gene IBA57 causes fatal infantile leukodystrophy.
DEBRAY, François-Guillaume ULg; Stumpfig, Claudia; Vanlander, Arnaud V. et al

in Journal of inherited metabolic disease (2015)

Leukodystrophies are a heterogeneous group of severe genetic neurodegenerative disorders. A multiple mitochondrial dysfunctions syndrome was found in an infant presenting with a progressive ... [more ▼]

Leukodystrophies are a heterogeneous group of severe genetic neurodegenerative disorders. A multiple mitochondrial dysfunctions syndrome was found in an infant presenting with a progressive leukoencephalopathy. Homozygosity mapping, whole exome sequencing, and functional studies were used to define the underlying molecular defect. Respiratory chain studies in skeletal muscle isolated from the proband revealed a combined deficiency of complexes I and II. In addition, western blotting indicated lack of protein lipoylation. The combination of these findings was suggestive for a defect in the iron-sulfur (Fe/S) protein assembly pathway. SNP array identified loss of heterozygosity in large chromosomal regions, covering the NFU1 and BOLA3, and the IBA57 and ABCB10 candidate genes, in 2p15-p11.2 and 1q31.1-q42.13, respectively. A homozygous c.436C > T (p.Arg146Trp) variant was detected in IBA57 using whole exome sequencing. Complementation studies in a HeLa cell line depleted for IBA57 showed that the mutant protein with the semi-conservative amino acid exchange was unable to restore the biochemical phenotype indicating a loss-of-function mutation of IBA57. In conclusion, defects in the Fe/S protein assembly gene IBA57 can cause autosomal recessive neurodegeneration associated with progressive leukodystrophy and fatal outcome at young age. In the affected patient, the biochemical phenotype was characterized by a defect in the respiratory chain complexes I and II and a decrease in mitochondrial protein lipoylation, both resulting from impaired assembly of Fe/S clusters. [less ▲]

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See detailMutation politiques et socioéconomiques latino-américaines
Santander, Sébastian ULg

Conference given outside the academic context (2009)

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See detailMutation update for the PORCN gene.
Lombardi, Maria Paola; BULK, Saskia ULg; Celli, Jacopo et al

in Human mutation (2011), 32(7), 723-8

Mutations in the PORCN gene were first identified in Goltz-Gorlin syndrome patients in 2007. Since then, several reports have been published describing a large variety of genetic defects resulting in the ... [more ▼]

Mutations in the PORCN gene were first identified in Goltz-Gorlin syndrome patients in 2007. Since then, several reports have been published describing a large variety of genetic defects resulting in the Goltz-Gorlin syndrome, and mutations or deletions were also reported in angioma serpiginosum, the pentalogy of Cantrell and Limb-Body Wall Complex. Here we present a review of the published mutations in the PORCN gene to date and report on seven new mutations together with the corresponding clinical data. Based on the review we have created a Web-based locus-specific database that lists all identified variants and allows the inclusion of future reports. The database is based on the Leiden Open (source) Variation Database (LOVD) software, and is accessible online at http://www.lovd.nl/porcn. At present, the database contains 106 variants, representing 68 different mutations, scattered along the whole coding sequence of the PORCN gene, and 12 large gene rearrangements, which brings up to 80 the number of unique mutations identified in Goltz-Gorlin syndrome patients. [less ▲]

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See detailMutational analysis of the catalytic centre of the Citrobacter freundii AmpD N-acetylmuramyl-L-alanine amidase
Genereux, Catherine ULg; Dehareng, Dominique ULg; Devreese, Bart et al

in Biochemical Journal (2004), 377(Pt 1), 111-120

Citrobacter freundii AmpD is an intracellular 1,6-anhydro-N-acetylmuramyl-L-alanine amidase involved in both peptidoglycan recycling and beta-lactamase induction. AmpD exhibits a strict specificity for 1 ... [more ▼]

Citrobacter freundii AmpD is an intracellular 1,6-anhydro-N-acetylmuramyl-L-alanine amidase involved in both peptidoglycan recycling and beta-lactamase induction. AmpD exhibits a strict specificity for 1,6-anhydromuropeptides and requires zinc for enzymic activity. The AmpD three-dimensional structure exhibits a fold similar to that of another Zn2+ N-acetylmuramyl-L-alanine amidase, the T7 lysozyme, and these two enzymes define a new family of Zn-amidases which can be related to the eukaryotic PGRP (peptidoglycan-recognition protein) domains. In an attempt to assign the different zinc ligands and to probe the catalytic mechanism of AmpD amidase, molecular modelling based on the NMR structure and site-directed mutagenesis were performed. Mutation of the two residues presumed to act as zinc ligands into alanine (H34A and D164A) yielded inactive proteins which had also lost their ability to bind zinc. By contrast, the active H154N mutant retained the capacity to bind the metal ion. Three other residues which could be involved in the AmpD catalytic mechanism have been mutated (Y63F, E116A, K162H and K162Q). The E116A mutant was inactive, but on the basis of the molecular modelling this residue is not directly involved in the catalytic mechanism, but rather in the binding of the zinc by contributing to the correct orientation of His-34. The K162H and K162Q mutants retained very low activity (0.7 and 0.2% of the wildtype activity respectively), whereas the Y63F mutant showed 16% of the wild-type activity. These three latter mutants exhibited a good affinity for Zn ions and the substituted residues are probably involved in the binding of the substrate. We also describe a new method for generating the N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-tripeptide AmpD substrate from purified peptidoglycan by the combined action of two hydrolytic enzymes. [less ▲]

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See detailMutational analysis of the p50 subunit of NF-kappa B and inhibition of NF-kappa B activity by trans-dominant p50 mutants.
Bressler, P.; Brown, K.; Timmer, W. et al

in Journal of Virology (1993), 67(1), 288-93

The NF-kappa B family of DNA-binding proteins regulates the expression of many cellular and viral genes. Each of these proteins has an N-terminal region that is homologous to the c-Rel proto-oncogene ... [more ▼]

The NF-kappa B family of DNA-binding proteins regulates the expression of many cellular and viral genes. Each of these proteins has an N-terminal region that is homologous to the c-Rel proto-oncogene product, and this Rel homology region defines both DNA binding and protein dimerization properties of the individual proteins. Most of the NF-kappa B family members have been shown to associate with themselves or with each other to form homodimers or heterodimers, and previous studies have shown that dimerization of NF-kappa B factors is necessary to provide a functional DNA binding domain. We have used site-directed mutagenesis to identify regions in the Rel homology domain of the p50/NF-kappa B protein that are important for DNA binding and protein dimerization. Our studies have identified mutations of p50 that interfere with DNA binding only and those that interfere with protein dimerization. Mutations of p50 which disrupt only DNA binding were still able to associate with other members of the NF-kappa B protein family. We demonstrate that such heterodimeric complexes inhibit transcriptional activation mediated in trans through a cis-acting kappa B motif; therefore, we have identified trans-dominant negative mutants of p50. [less ▲]

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See detailMutational Analysis Of The Tre2 Oncogene Encoding An Inactive Rabgap
Bizimungu, C.; Thomas, Annick ULg; Brasseur, Robert ULg et al

in Biotechnology Letters (2007), 29(12), 1927-37

The TRE2 oncoprotein is structurally related to the RabGAP (GTPase-activating protein) family. However, TRE2 seems enzymatically inactive. Two regions are important for its lack of GAP activity. First ... [more ▼]

The TRE2 oncoprotein is structurally related to the RabGAP (GTPase-activating protein) family. However, TRE2 seems enzymatically inactive. Two regions are important for its lack of GAP activity. First, the TBC domain, forming the catalytically active domain of RabGAPs, is non-functional in the oncoprotein. Also involved in TRE2 inactivity is the 93-aa region flanking the TBC domain on the C-terminal side. In order to identify the residues responsible for non-functionality, we performed hydrophobic cluster analysis of the oncoprotein sequence, combined with secondary structure prediction, receptor-binding domain analysis, and a tilted peptide calculation. These analyses were complemented with site-directed and random mutagenesis experiments. On the basis of our data, we hypothesize that the lack of secondary structure of the region flanking the TBC domain in TRE2 may explain why this region plays a role in the lack of GAP activity, even when a potentially functional TBC domain is present. [less ▲]

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See detailMutational analysis of the two zinc-binding sites of the Bacillus cereus 569/H/9 metallo-beta-lactamase
De Seny, Dominique ULg; Prosperi, Christelle ULg; Bebrone, Carine ULg et al

in Biochemical Journal (2002), 363(Pt 3), 687-696

The metallo-beta-lactamase BcII from Bacillus cereus 569/H/9 possesses a binuclear zinc centre. The mono-zinc form of the enzyme displays an appreciably high activity. although full efficiency is observed ... [more ▼]

The metallo-beta-lactamase BcII from Bacillus cereus 569/H/9 possesses a binuclear zinc centre. The mono-zinc form of the enzyme displays an appreciably high activity. although full efficiency is observed for the di-zinc enzyme. In an attempt to assign the involvement of the different zinc ligands in the catalytic properties of BcII, individual substitutions of selected amino acids were generated. With the exception of His(116) --> Ser (H116S), C221A and C221S, the mono- and di-zinc forms of all the other mutants were poorly active. The activity of H116S decreases by a factor of 10 when compared with the wild type. The catalytic efficiency of C221A and C221S was zinc-dependent. The monozinc forms of these mutants exhibited a low activity, whereas the catalytic efficiency of their respective di-zinc forms was comparable with that of the wild type. Surprisingly, the zinc contents of the mutants and the wild-type Bell were similar. These data suggest that the affinity of the beta-lactamase for the metal was not affected by the substitution of the ligand. The pH-dependence of the H196S catalytic efficiency indicates that the zinc ions participate in the hydrolysis of the beta-lactam ring by acting as a Lewis acid. The zinc ions activate the catalytic water molecule, but also polarize the carbonyl bond of the beta-lactam ring and stabilize the development of a negative charge on the carbonyl oxygen of the tetrahedral reaction intermediate. Our studies also demonstrate that Asn(233) is not directly involved in the interaction with the substrates. [less ▲]

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See detailMutational analysis of the zinc- and substrate-binding sites in the CphA metallo-beta-lactamase from Aeromonas hydrophila.
Bebrone, Carine ULg; Anne, Christine; Kerff, Frédéric ULg et al

in Biochemical Journal (2008), 414(1), 151-9

The subclass B2 CphA (Carbapenemase hydrolysing Aeromonas) beta-lactamase from Aeromonas hydrophila is a Zn(2+)-containing enzyme that specifically hydrolyses carbapenems. In an effort to evaluate ... [more ▼]

The subclass B2 CphA (Carbapenemase hydrolysing Aeromonas) beta-lactamase from Aeromonas hydrophila is a Zn(2+)-containing enzyme that specifically hydrolyses carbapenems. In an effort to evaluate residues potentially involved in metal binding and/or catalysis (His(118), Asp(120), His(196) and His(263)) and in substrate specificity (Val(67), Thr(157), Lys(224) and Lys(226)), site-directed mutants of CphA were generated and characterized. Our results confirm that the first zinc ion is in interaction with Asp(120) and His(263), and thus is located in the 'cysteine' zinc-binding site. His(118) and His(196) residues seem to be interacting with the second zinc ion, as their replacement by alanine residues has a negative effect on the affinity for this second metal ion. Val(67) plays a significant role in the binding of biapenem and benzylpenicillin. The properties of a mutant with a five residue (LFKHV) insertion just after Val(67) also reveals the importance of this region for substrate binding. This latter mutant has a higher affinity for the second zinc ion than wild-type CphA. The T157A mutant exhibits a significantly modified activity spectrum. Analysis of the K224Q and N116H/N220G/K224Q mutants suggests a significant role for Lys(224) in the binding of substrate. Lys(226) is not essential for the binding and hydrolysis of substrates. Thus the present paper helps to elucidate the position of the second zinc ion, which was controversial, and to identify residues important for substrate binding. [less ▲]

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See detailMutational analysis of varicella-zoster virus major immediate-early protein IE62
Baudoux, Laurence; Defechereux, Patricia; Schoonbroodt, Sonia et al

in Nucleic Acids Research (1995), 23(8), 1341-1349

The varicella-zoster virus (VZV) open reading frame 62 encodes an immediate-early protein (IE62) that transactivates expression of various VZV promoters and autoregulates its own expression in transient ... [more ▼]

The varicella-zoster virus (VZV) open reading frame 62 encodes an immediate-early protein (IE62) that transactivates expression of various VZV promoters and autoregulates its own expression in transient expression assays. In Vero cells, IE62 was shown to transactivate the expression of all putative immediate-early (IE) and early (E) genes of VZV with an up-regulating effect at low intracellular concentrations. To define the functional domains involved in the regulatory properties of IE62, a large number of in-frame insertions and deletions were introduced into a plasmid-borne copy of the gene encoding IE62. Studies of the regulatory activities of the resultant mutant polypeptides in transient expression assays allowed to delineate protein regions important for repression of its own promoter and for transactivation of a VZV putative immediate-early gene (ORF61) promoter and an early gene (ORF29) promoter. This mutational analysis resulted in the identification of a new functional domain situated at the border between regions 4 and 5 which plays a crucial role in the IE62 regulatory functions. This domain turned out to be very well conserved amongst homologous alphaherpesvirus regulatory proteins and appeared to be rich in bulky hydrophobic and proline residues, similar to the proline-rich region of the CAAT box binding protein CTF-1. By immunofluorescence, a nuclear localization signal has been mapped in region 3. [less ▲]

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See detailMutational analysis of VIM-2 reveals an essential determinant for metallo-beta-lactamase stability and folding.
Borgianni, Luisa; Vandenameele, Julie ULg; Matagne, André ULg et al

in Antimicrobial Agents and Chemotherapy (2010), 54(8), 3197-204

Metallo-beta-lactamase (MBL)-producing bacteria are emerging worldwide and represent a formidable threat to the efficacy of relevant beta-lactams, including carbapenems, expanded-spectrum cephalosporins ... [more ▼]

Metallo-beta-lactamase (MBL)-producing bacteria are emerging worldwide and represent a formidable threat to the efficacy of relevant beta-lactams, including carbapenems, expanded-spectrum cephalosporins, and beta-lactamase inactivator/beta-lactam combinations. VIM-2 is currently the most widespread MBL and represents a primary target for MBL inhibitor research, the clinical need for which is expected to further increase in the future. Using a saturation mutagenesis approach, we probed the importance of four residues (Phe-61, Ala-64, Tyr-67, and Trp-87) located close to the VIM-2 active site and putatively relevant to the enzyme activity based on structural knowledge of the enzyme and on structure-activity relationships of the subclass B1 MBLs. The ampicillin MIC values shown by the various mutants were affected very differently depending on the randomized amino acid position. Position 64 appeared to be rather tolerant to substitution, and kinetic studies showed that the A64W mutation did not significantly affect substrate hydrolysis or binding, representing an important difference from IMP-type enzymes. Phe-61 and Tyr-67 could be replaced with several amino acids without the ampicillin MIC being significantly affected, but in contrast, Trp-87 was found to be critical for ampicillin resistance. Further kinetic and biochemical analyses of W87A and W87F variants showed that this residue is apparently important for the structure and proper folding of the enzyme but, surprisingly, not for its catalytic activity. These data support the critical role of residue 87 in the stability and folding of VIM-2 and might have strong implications for MBL inhibitor design, as this residue would represent an ideal target for interaction with small molecules. [less ▲]

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