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See detailCrystal structure of the Actinomadura R39 DD-peptidase reveals new domains in penicillin-binding proteins.
Sauvage, Eric ULg; Herman, Raphaël ULg; Petrella, Stephanie et al

in Journal of Biological Chemistry (2005), 280(35), 31249-56

Actinomadura sp. R39 produces an exocellular DD-peptidase/penicillin-binding protein (PBP) whose primary structure is similar to that of Escherichia coli PBP4. It is characterized by a high beta-lactam ... [more ▼]

Actinomadura sp. R39 produces an exocellular DD-peptidase/penicillin-binding protein (PBP) whose primary structure is similar to that of Escherichia coli PBP4. It is characterized by a high beta-lactam-binding activity (second order rate constant for the acylation of the active site serine by benzylpenicillin: k2/K = 300 mm(-1) s(-1)). The crystal structure of the DD-peptidase from Actinomadura R39 was solved at a resolution of 1.8 angstroms by single anomalous dispersion at the cobalt resonance wavelength. The structure is composed of three domains: a penicillin-binding domain similar to the penicillin-binding domain of E. coli PBP5 and two domains of unknown function. In most multimodular PBPs, additional domains are generally located at the C or N termini of the penicillin-binding domain. In R39, the other two domains are inserted in the penicillin-binding domain, between the SXXK and SXN motifs, in a manner similar to "Matryoshka dolls." One of these domains is composed of a five-stranded beta-sheet with two helices on one side, and the other domain is a double three-stranded beta-sheet inserted in the previous domain. Additionally, the 2.4-angstroms structure of the acyl-enzyme complex of R39 with nitrocefin reveals the absence of active site conformational change upon binding the beta-lactams. [less ▲]

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See detailCrystal structure of the Bacillus subtilis penicillin-binding protein 4a, and its complex with a peptidoglycan mimetic peptide
Sauvage, Eric ULg; Duez, Colette ULg; Herman, Raphaël ULg et al

in Journal of Molecular Biology (2007), 371(2), 528-539

The genome of Bacillus subtilis encodes 16 penicillin-binding proteins (PBPs) involved in the synthesis and/or remodelling of the peptidoglycan during the complex life cycle of this sporulating Gram ... [more ▼]

The genome of Bacillus subtilis encodes 16 penicillin-binding proteins (PBPs) involved in the synthesis and/or remodelling of the peptidoglycan during the complex life cycle of this sporulating Gram-positive rod-shaped bacterium. PBP4a (encoded by the dacC gene) is a low-molecular mass PBP clearly exhibiting in vitro DD-carboxypeptidase activity. We have solved the crystal structure of this protein alone and in complex with a peptide (D-alpha'-aminopymelyl-epsilon-D-alanyl-D-alanine) that mimics the C-terminal end of the Bacillus peptidoglycan stem peptide. PBP4a is composed of three domains: the penicillin-binding domain with a fold similar to the class A 13-lactamase structure and two domains inserted between the conserved motifs 1 and 2 characteristic of the penicillin-recognizing enzymes. The soaking of PBP4a in a solution Of D-alpha-aminopymelyl-epsilon-D-alanyl-D-alanine resulted in an adduct between PBP4a and a D-alpha-aminopimelyl-epsilon-D-alanine dipeptide and an unbound D-alanine, i.e. the products of acylation of PBP4a by D-alpha-aminopymelyl-epsilon-D-alanyl-D-alanine with the release of a D-alanine. The adduct also reveals a binding pocket specific to the diaminopimelic acid, the third residue of the peptidoglycan stem pentapeptide of B. subtilis. This pocket is specific for this class of PBPs. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailCrystal structure of the C47S mutant of human peroxiredoxin 5
Evrard, Christine ULg; Smeets, Aude; Knoops, Bernard et al

in Journal of Chemical Crystallography (2004), 34

In the crystal structure of the reduced form of the wild-type human peroxiredoxin 5, the presence of a benzoate ion in direct interaction with the peroxidatic cysteine (Cys 47) appeared as a rather ... [more ▼]

In the crystal structure of the reduced form of the wild-type human peroxiredoxin 5, the presence of a benzoate ion in direct interaction with the peroxidatic cysteine (Cys 47) appeared as a rather intriguing feature since it is known that the benzoate ion can play the role of a specific hydroxyl radical scavenger. The crystal structure of the C47S mutant of the same enzyme has been crystallized in the tetragonal system, space group P41212, with a = 65.65 Å, c = 122.04 Å. It confirms the presence of this benzoate ion in spite of the mutation into a serine of the Cys 47 residue to which the benzoate ion was directly linked in the wild-type structure. The benzoate ion seems to be stabilized by hydrophobic contacts on both sides of the aromatic ring. In this matter, the α5 helix, which is specific to peroxiredoxin 5 among mammalian peroxiredoxins, plays an important role. These hydrophobic contacts also allow to suggest why the benzoate ion disappears when the molecule is oxidized. [less ▲]

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See detailCrystal structure of the catalytic domain of MMP-16/MT3-MMP: Characterization of MT-MMP specific features
Lang, R.; Braun, M.; Sounni, Nor Eddine ULg et al

in Journal of Molecular Biology (2004), 336(1), 213-225

Membrane-type matrix metalloproteinases (MT-MMPs) have attracted strong attention, because four of them can activate a key player in the tumor scenario, proMMP-2/progelatinase A. In addition to this ... [more ▼]

Membrane-type matrix metalloproteinases (MT-MMPs) have attracted strong attention, because four of them can activate a key player in the tumor scenario, proMMP-2/progelatinase A. In addition to this indirect effect on the cellular environment, these MT-MMPs degrade extracellular matrix proteins, and their overproduction is associated with tumor growth. We have solved the structure of the catalytic domain (cd) of MT3-MMP/MMP-16 in complex with the hydroxamic acid inhibitor batimastat. CdMT3-MMP exhibits a classical MMP-fold with similarity to MT1-MMP. Nevertheless, it also shows unique properties such as a modified MT-specific loop and a closed S1' specificity pocket, which might help to design specific inhibitors. Some MT-MMP-specific features, derived from the crystal structures of MT-1-MMP determined previously and MT3-MMP, and revealed in recent mutagenesis experiments, explain the impaired interaction of the MT-MMPs with TIMP-1. Docking experiments with proMMP-2 show some exposed loops including the MT-loop of cdMT3-MMP involved in the interaction with the proMMP-2 prodomain in the activation encounter complex. This model might help to understand the experimentally proven importance of the MT-loop for the activation of proMMP-2. (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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See detailThe crystal structure of the cell division amidase AmiC reveals the fold of the AMIN domain, a new peptidoglycan binding domain.
Rocaboy, Mathieu; Herman, Raphael; Sauvage, Eric ULg et al

in Molecular microbiology (2013)

Binary fission is the ultimate step of the prokaryotic cell cycle. In Gram-negative bacteria like Escherichia coli, this step implies the invagination of three biological layers (cytoplasmic membrane ... [more ▼]

Binary fission is the ultimate step of the prokaryotic cell cycle. In Gram-negative bacteria like Escherichia coli, this step implies the invagination of three biological layers (cytoplasmic membrane, peptidoglycan and outer membrane), biosynthesis of the new poles and eventually, daughter cells separation. The latter requires the coordinated action of the N-acetylmuramyl-L-alanine amidases AmiA/B/C and their LytM activators EnvC and NlpD to cleave the septal peptidoglycan. We present here the 2.5 A crystal structure of AmiC which includes the first report of an AMIN domain structure, a beta-sandwich of two symmetrical four-stranded beta-sheets exposing highly conserved motifs on the two outer faces. We show that this N-terminal domain, involved in the localization of AmiC at the division site, is a new peptidoglycan-binding domain. The C-terminal catalytic domain shows an auto-inhibitory alpha helix obstructing the active site. AmiC lacking this helix exhibits by itself an activity comparable to that of the wild type AmiC activated by NlpD. We also demonstrate the interaction between AmiC and NlpD by microscale thermophoresis and confirm the importance of the active site blocking alpha helix in the regulation of the amidase activity. [less ▲]

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See detailCrystal structure of the cold-active aminopeptidase from Colwellia psychrerythraea, a close structural homologue of the human bifunctional leukotriene A4 hydrolase
Bauvois, Cédric; Jacquamet, Lilian; Huston, Adrienne L. et al

in Journal of Biological Chemistry (2008), 283(34), 23315-25

The crystal structure of a cold-active aminopeptidase (ColAP) from Colwellia psychrerythraea strain 34H has been determined, extending the number of crystal structures of the M1 metallopeptidase family to ... [more ▼]

The crystal structure of a cold-active aminopeptidase (ColAP) from Colwellia psychrerythraea strain 34H has been determined, extending the number of crystal structures of the M1 metallopeptidase family to four among the 436 members currently identified. In agreement with their sequence similarity, the overall structure of ColAP displayed a high correspondence with leukotriene A4 hydrolase (LTA4H), a human bifunctional enzyme that converts leukotriene A4 (LTA4) in the potent chemoattractant leukotriene B4. Indeed, both enzymes are composed of three domains, an N-terminal saddle-like domain, a catalytic thermolysin-like domain, and a less conserved C-terminal alpha-helical flat spiral domain. Together, these domains form a deep cavity harboring the zinc binding site formed by residues included in the conserved HEXXHX(18)H motif. A detailed structural comparison of these enzymes revealed several plausible determinants of ColAP cold adaptation. The main differences involve specific amino acid substitutions, loop content and solvent exposure, complexity and distribution of ion pairs, and differential domain flexibilities. Such elements may act synergistically to allow conformational flexibility needed for an efficient catalysis in cold environments. Furthermore, the region of ColAP corresponding to the aminopeptidase active site of LTA4H is much more conserved than the suggested LTA4 substrate binding region. This observation supports the hypothesis that this region of the LTA4H active site has evolved in order to fit the lipidic substrate. [less ▲]

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See detailCrystal structure of the EF-hand parvalbumin at atomic resolution (0.91 Å) and at low temperature (100 K). Evidence for conformational multistates within the hydrophobic core.
Declercq, Jean-Paul; Evrard, Christine ULg; Lamzin, Victor et al

in Protein Science : A Publication of the Protein Society (1999), 8

Several crystal structures of parvalbumin (Parv), a typical EF-hand protein, have been reported so far for different species with the best resolution achieving 1.5 Å. Using a crystal grown under ... [more ▼]

Several crystal structures of parvalbumin (Parv), a typical EF-hand protein, have been reported so far for different species with the best resolution achieving 1.5 Å. Using a crystal grown under microgravity conditions, cryotechniques (100 K), and synchrotron radiation, it has now been possible to determine the crystal structure of the fully Ca2+ loaded form of pike (component pI 4.10) Parv.Ca2 at atomic resolution (0.91 Å). The availability of such a high quality structure offers the opportunity to contribute to the definition of the validation tools useful for the refinement of protein crystal structures determined to lower resolution. Besides a better definition of most of the elements in the protein threedimensional structure than in previous studies, the high accuracy thus achieved allows the detection of well-defined alternate conformations, which are observed for 16 residues out of 107 in total. Among them, six occupy an internal position within the hydrophobic core and converge toward two small buried cavities with a total volume of about 60 Å3. There is no indication of any water molecule present in these cavities. It is probable that at temperatures of physiological conditions there is a dynamic interconversion between these alternate conformations in an energy-barrier dependent manner. Such motions for which the amplitudes are provided by the present study will be associated with a timedependent remodeling of the void internal space as part of a slow dynamics regime (millisecond timescales) of the parvalbumin molecule. The relevance of such internal dynamics to function is discussed. [less ▲]

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See detailCrystal Structure of the Extended-Spectrum β -Lactamase PER-2 and Insights into the Role of Specific Residues in the Interaction with β -Lactams and β -Lactamase Inhibitors
Ruggiero, Melina; Kerff, Frédéric ULg; Herman, Raphaël ULg et al

in Antimicrobial Agents and Chemotherapy (2014), 58(10), 5994-6002

PER-2 belongs to a small (7 members to date) group of extended-spectrum beta-lactamases. It has 88% amino acid identity with PER-1 and both display high catalytic efficiencies toward most beta-lactams. In ... [more ▼]

PER-2 belongs to a small (7 members to date) group of extended-spectrum beta-lactamases. It has 88% amino acid identity with PER-1 and both display high catalytic efficiencies toward most beta-lactams. In this study, we determined the X-ray structure of PER-2 at 2.20 A and evaluated the possible role of several residues in the structure and activity toward beta-lactams and mechanism-based inhibitors. PER-2 is defined by the presence of a singular trans bond between residues 166 to 167, which generates an inverted Omega loop, an expanded fold of this domain that results in a wide active site cavity that allows for efficient hydrolysis of antibiotics like the oxyimino-cephalosporins, and a series of exclusive interactions between residues not frequently involved in the stabilization of the active site in other class A beta-lactamases. PER beta-lactamases might be included within a cluster of evolutionarily related enzymes harboring the conserved residues Asp136 and Asn179. Other signature residues that define these enzymes seem to be Gln69, Arg220, Thr237, and probably Arg/Lys240A ("A" indicates an insertion according to Ambler's scheme for residue numbering in PER beta-lactamases), with structurally important roles in the stabilization of the active site and proper orientation of catalytic water molecules, among others. We propose, supported by simulated models of PER-2 in combination with different beta-lactams, the presence of a hydrogen-bond network connecting Ser70-Gln69-water-Thr237-Arg220 that might be important for the proper activity and inhibition of the enzyme. Therefore, we expect that mutations occurring in these positions will have impacts on the overall hydrolytic behavior. [less ▲]

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See detailCrystal Structure of the Lysozyme from Bacteriophage Lambda and its Relationship with V and C-type Lysozymes
Evrard, Christine ULg; Fastrez, Jacques; Declercq, Jean-Paul

in Journal of Molecular Biology (1998), 276

Like other lysozymes, the bacteriophage lambda lysozyme is involved in the digestion of bacterial walls. This enzyme is remarkable in that its mechanism of action is different from the classical lysozyme ... [more ▼]

Like other lysozymes, the bacteriophage lambda lysozyme is involved in the digestion of bacterial walls. This enzyme is remarkable in that its mechanism of action is different from the classical lysozyme's mechanism. From the point of view of protein evolution, it shows features of lysozymes from different classes. The crystal structure of the enzyme in which all tryptophan residues have been replaced by aza-tryptophan has been solved by X-ray crystallography at 2.3 Å using a combination of multiple isomorphous replacement, non-crystallographic symmetry averaging and density modification techniques. There are three molecules in the asymmetric unit. The characteristic structural elements of lysozymes are conserved: each molecule is organized in two domains connected by a helix and the essential catalytic residue (Glu19) is located in the depth of a cleft between the two domains. This cleft shows an open conformation in two of the independent molecules, while access to the cavity is much more restricted in the last one. A structural alignment with T4 lysozyme and hen egg white lysozyme allows us to superpose about 60 Cα atoms with a rms distance close to 2 Å. The best alignments concern the helix preceding the catalytic residue, some parts of the beta sheets and the helix joining the two domains. The results of sequence alignments with the V and C lysozymes, in which weak local similarities had been detected, are compared with the structural results. [less ▲]

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See detailCrystal structure of the Mycobacterium fortuitum class A beta-lactamase: structural basis for broad substrate specificity.
Sauvage, Eric ULg; Fonze, Eveline; Quinting, Birgit et al

in Antimicrobial Agents and Chemotherapy (2006), 50(7), 2516-21

beta-Lactamases are the main cause of bacterial resistance to penicillins and cephalosporins. Class A beta-lactamases, the largest group of beta-lactamases, have been found in many bacterial strains ... [more ▼]

beta-Lactamases are the main cause of bacterial resistance to penicillins and cephalosporins. Class A beta-lactamases, the largest group of beta-lactamases, have been found in many bacterial strains, including mycobacteria, for which no beta-lactamase structure has been previously reported. The crystal structure of the class A beta-lactamase from Mycobacterium fortuitum (MFO) has been solved at 2.13-A resolution. The enzyme is a chromosomally encoded broad-spectrum beta-lactamase with low specific activity on cefotaxime. Specific features of the active site of the class A beta-lactamase from M. fortuitum are consistent with its specificity profile. Arg278 and Ser237 favor cephalosporinase activity and could explain its broad substrate activity. The MFO active site presents similarities with the CTX-M type extended-spectrum beta-lactamases but lacks a specific feature of these enzymes, the VNYN motif (residues 103 to 106), which confers on CTX-M-type extended-spectrum beta-lactamases a more efficient cefotaximase activity. [less ▲]

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See detailCrystal structure of the sensor domain of the BlaR penicillin receptor from Bacillus licheniformis
Kerff, Frédéric ULg; Charlier, Paulette ULg; Colombo, Maria Louisa et al

in Biochemistry (2003), 42(44), 12835-12843

As in several staphylococci, the synthesis of the Bacillus licheniformis 749/I beta-lactamase is an inducible phenomenon regulated by a signal-transducing membrane protein BlaR. The C-terminal domain of ... [more ▼]

As in several staphylococci, the synthesis of the Bacillus licheniformis 749/I beta-lactamase is an inducible phenomenon regulated by a signal-transducing membrane protein BlaR. The C-terminal domain of this multimodular protein is an extracellular domain which specifically recognizes beta-lactam antibiotics. When it binds a beta-lactam, a signal is transmitted by the transmembrane region to the intracellular loops. In response, the hydrolytic activity of the BlaR large cytoplasmic L3 loop is induced, and a cascade of reactions is generated, leading to the transcription of the beta-lactamase gene. Here, we describe the crystal structure of the extracellular penicillin-receptor domain of BlaR (residues 346-601) at 2.5 Angstrom resolution in order to understand why this domain, whose folding is very similar to that of class D beta-lactamases, behaves as a highly sensitive penicillin-binding protein rather than a beta-lactamase. Two residues of the BlaR C-terminal domain, Thr452 and Thr542, modify the hydrophobic characteristic of the class D beta-lactamase active site. Both residues seem to be in part responsible for the lack of beta-lactamase activity of the BlaR protein due to the stability of the acyl-enzyme. Although further experimental data are needed to fully understand the transmembrane induction process, the comparison of the BlaR sensor domain structure with those of class D beta-lactamase complexes and penicillin-binding proteins provides interesting elements to hypothesize on possible signal transmission mechanisms. [less ▲]

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See detailThe crystal structure of the β-lactamase of Streptomyces albus G at 0.3 nm resolution
Dideberg, Otto; Charlier, Paulette ULg; Wery, Jean-Paul et al

in Biochemical Journal (1987), 245(3), 911-913

The crystal structure of the beta-lactamase of Streptomyces albus G has been solved at 0.3 nm resolution by X-ray-diffraction methods. The enzyme is a typical two-domain protein. One domain consists of ... [more ▼]

The crystal structure of the beta-lactamase of Streptomyces albus G has been solved at 0.3 nm resolution by X-ray-diffraction methods. The enzyme is a typical two-domain protein. One domain consists of five alpha-helices, and the other is five-stranded beta-sheet with alpha-helices on both sides of the sheet. The active-site serine residue (Ser-48) is within a cleft located between the two domains. [less ▲]

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See detailThe crystal structure of triosephosphate isomerase (TIM) from Thermotoga maritima: a comparative thermostability structural analysis of ten different TIM structures
Maes, Dominique; Zeelen, Johan P.; Thanki, Narmada et al

in Proteins (1999), 37(3), 441-53

The molecular mechanisms that evolution has been employing to adapt to environmental temperatures are poorly understood. To gain some further insight into this subject we solved the crystal structure of ... [more ▼]

The molecular mechanisms that evolution has been employing to adapt to environmental temperatures are poorly understood. To gain some further insight into this subject we solved the crystal structure of triosephosphate isomerase (TIM) from the hyperthermophilic bacterium Thermotoga maritima (TmTIM). The enzyme is a tetramer, assembled as a dimer of dimers, suggesting that the tetrameric wild-type phosphoglycerate kinase PGK-TIM fusion protein consists of a core of two TIM dimers covalently linked to 4 PGK units. The crystal structure of TmTIM represents the most thermostable TIM presently known in its 3D-structure. It adds to a series of nine known TIM structures from a wide variety of organisms, spanning the range from psychrophiles to hyperthermophiles. Several properties believed to be involved in the adaptation to different temperatures were calculated and compared for all ten structures. No sequence preferences, correlated with thermal stability, were apparent from the amino acid composition or from the analysis of the loops and secondary structure elements of the ten TIMs. A common feature for both psychrophilic and T. maritima TIM is the large number of salt bridges compared with the number found in mesophilic TIMs. In the two thermophilic TIMs, the highest amount of accessible hydrophobic surface is buried during the folding and assembly process. [less ▲]

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See detailCrystal structure of trisodium iron diphosphate, Na2.88Fe(PO4)(2), a synthetic phosphate with hannayite-type heteropolyhedral chains
Hatert, Frédéric ULg

in Zeitschrift für Kristallographie. New Crystal Structures (2007), 222(1), 6-8

FeNa2.88O8P2, triclinic, P (1) over bar (no. 2), a 5.3141(6) b = 8.5853(9) angstrom, c = 8.7859(8) angstrom, alpha = 114.429(9)degrees, beta = 92.327(9)degrees, gamma = 106.08(1)degrees, V = 345.1 ... [more ▼]

FeNa2.88O8P2, triclinic, P (1) over bar (no. 2), a 5.3141(6) b = 8.5853(9) angstrom, c = 8.7859(8) angstrom, alpha = 114.429(9)degrees, beta = 92.327(9)degrees, gamma = 106.08(1)degrees, V = 345.1 angstrom(3),Z = 2, Rgt(F) = 0.028, wR(ref)(F-2) = 0.087, T = 293 K. [less ▲]

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See detailCrystal structures of complexes of bacterial DD-peptidases with peptidoglycan-mimetic ligands: the substrate specificity puzzle.
Sauvage, Eric ULg; Powell, Ailsa J; Heilemann, Jason et al

in Journal of Molecular Biology (2008), 381(2), 383-93

The X-ray crystal structures of covalent complexes of the Actinomadura R39 dd-peptidase and Escherichia coli penicillin-binding protein (PBP) 5 with beta-lactams bearing peptidoglycan-mimetic side chains ... [more ▼]

The X-ray crystal structures of covalent complexes of the Actinomadura R39 dd-peptidase and Escherichia coli penicillin-binding protein (PBP) 5 with beta-lactams bearing peptidoglycan-mimetic side chains have been determined. The structure of the hydrolysis product of an analogous peptide bound noncovalently to the former enzyme has also been obtained. The R39 DD-peptidase structures reveal the presence of a specific binding site for the D-alpha-aminopimelyl side chain, characteristic of the stem peptide of Actinomadura R39. This binding site features a hydrophobic cleft for the pimelyl methylene groups and strong hydrogen bonding to the polar terminus. Both of these active site elements are provided by amino acid side chains from two separate domains of the protein. In contrast, no clear electron density corresponding to the terminus of the peptidoglycan-mimetic side chains is present when these beta-lactams are covalently bound to PBP5. There is, therefore, no indication of a specific side-chain binding site in this enzyme. These results are in agreement with those from kinetics studies published earlier and support the general prediction made at the time of a direct correlation between kinetics and structural evidence. The essential high-molecular-mass PBPs have demonstrated, to date, no specific reactivity with peptidoglycan-mimetic peptide substrates and beta-lactam inhibitors and, thus, probably do not possess a specific substrate-binding site of the type demonstrated here with the R39 DD-peptidase. This striking deficiency may represent a sophisticated defense mechanism against low-molecular-mass substrate-analogue inhibitors/antibiotics; its discovery should focus new inhibitor design. [less ▲]

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See detailCrystal structures of oxidized and reduced forms of human mitochondrial thioredoxin 2
Smeets, Aude; Evrard, Christine ULg; Landtmeters, Marie et al

in Protein Science : A Publication of the Protein Society (2005), 14

Mammalian thioredoxin 2 is a mitochondrial isoform of highly evolutionary conserved thioredoxins. Thioredoxins are small ubiquitous protein–disulfide oxidoreductases implicated in a large variety of ... [more ▼]

Mammalian thioredoxin 2 is a mitochondrial isoform of highly evolutionary conserved thioredoxins. Thioredoxins are small ubiquitous protein–disulfide oxidoreductases implicated in a large variety of biological functions. In mammals, thioredoxin 2 is encoded by a nuclear gene and is targeted to mitochondria by a N-terminal mitochondrial presequence. Recently, mitochondrial thioredoxin 2 was shown to interact with components of the mitochondrial respiratory chain and to play a role in the control of mitochondrial membrane potential, regulating mitochondrial apoptosis signaling pathway. Here we report the first crystal structures of a mammalian mitochondrial thioredoxin 2. Crystal forms of reduced and oxidized human thioredoxin 2 are described at 2.0 and 1.8A ˚ resolution. Though the folding is rather similar to that of human cytosolic/nuclear thioredoxin 1, important differences are observed during the transition between the oxidized and the reduced states of human thioredoxin 2, compared with human thioredoxin 1. In spite of the absence of the Cys residue implicated in dimer formation in human thioredoxin 1, dimerization still occurs in the crystal structure of human thioredoxin 2, mainly mediated by hydrophobic contacts, and the dimers are associated to form two-dimensional polymers. Interestingly, the structure of human thioredoxin 2 reveals possible interaction domains with human peroxiredoxin 5, a substrate protein of human thioredoxin 2 in mitochondria. [less ▲]

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See detailCrystal structures of the Bacillus licheniformis BS3 class A beta-lactamase and of the acyl-enzyme adduct formed with cefoxitin
Fonzé, Evelyne; Vanhove, Mac; Dive, Georges ULg et al

in Biochemistry (2002), 41(6), 1877-1885

The Bacillus licheniformis BS3 beta-lactamase catalyzes the hydrolysis of the beta-lactam ring of penicillins, cephalosporins, and related compounds. The production of beta-lactamases is the most common ... [more ▼]

The Bacillus licheniformis BS3 beta-lactamase catalyzes the hydrolysis of the beta-lactam ring of penicillins, cephalosporins, and related compounds. The production of beta-lactamases is the most common and thoroughly studied cause of antibiotic resistance. Although they escape the hydrolytic activity of the prototypical Staphylococcus aureus beta-lactamase, many cephems are good substrates for a large number of beta-lactamases. However, the introduction of a 7alpha-methoxy substituent, as in cefoxitin, extends their antibacterial spectrum to many cephalosporin-resistant Gram-negative bacteria. The 7alphamethoxy group selectively reduces the hydrolytic action of many beta-lactamases without having a significant effect on the affinity for the target enzymes, the membrane penicillin-binding proteins. We report here the crystallographic structures of the BS3 enzyme and its acyl-enzyme adduct with cefoxitin at 1.7 Angstrom resolution. The comparison of the two structures reveals a covalent acyl-enzyme adduct with perturbed active site geometry, involving a different conformation of the Omega-loop that bears the essential catalytic Glu166 residue. This deformation is induced by the cefoxitin side chain whose position is constrained by the presence of the alpha-methoxy group. The hydrolytic water molecule is also removed from the active site by the 7beta-carbonyl of the acyl intermediate. In light of the interactions and steric hindrances in the active site of the structure of the BS3-cefoxitin acyl-enzyme adduct, the crucial role of the conserved Asn132 residue is confirmed and a better understanding of the kinetic results emerges. [less ▲]

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See detailCrystal structures of the psychrophilic a-amylase from Alteromonas haloplanctis in its native form and complexed with an inhibitor
Aghajari, N.; Feller, Georges ULg; Gerday, Charles ULg et al

in Protein Science : A Publication of the Protein Society (1998), 7(6), 564-572

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