| 1. |
- Fullam, Elizabeth, et al.
(författare)
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Structure and function of the transketolase from Mycobacterium tuberculosis and comparison with the human enzyme
- 2012
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Ingår i: Open Biology. - : The Royal Society. - 2046-2441. ; 2, s. 110026-
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Tidskriftsartikel (refereegranskat)abstract
- The transketolase (TKT) enzyme in Mycobacterium tuberculosis represents a novel drug target for tuberculosis treatment and has low homology with the orthologous human enzyme. Here, we report on the structural and kinetic characterization of the transketolase from M. tuberculosis (TBTKT), a homodimer whose monomers each comprise 700 amino acids. We show that TBTKT catalyses the oxidation of donor sugars xylulose-5-phosphate and fructose-6-phosphate as well as the reduction of the acceptor sugar ribose-5-phosphate. An invariant residue of the TKT consensus sequence required for thiamine cofactor binding is mutated in TBTKT; yet its catalytic activities are unaffected, and the 2.5 angstrom resolution structure of full-length TBTKT provides an explanation for this. Key structural differences between the human and mycobacterial TKT enzymes that impact both substrate and cofactor recognition and binding were uncovered. These changes explain the kinetic differences between TBTKT and its human counterpart, and their differential inhibition by small molecules. The availability of a detailed structural model of TBTKT will enable differences between human and M. tuberculosis TKT structures to be exploited to design selective inhibitors with potential antitubercular activity.
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| 2. |
- Jansson, Anna M., 1979-
(författare)
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Targeting Infectious Disease : Structural and functional studies of proteins from two RNA viruses and Mycobacterium tuberculosis
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The recent emergence of a number of new viral diseases as well as the re-emergence of tuberculosis (TB), indicate an urgent need for new drugs against viral and bacterial infections.Coronavirus nsp1 has been shown to induce suppression of host gene expression and interfere with host immune response. However, the mechanism behind this is currently unknown. Here we present the first nsp1 structure from an alphacoronavirus, Transmissible gastroenteritis virus (TGEV) nsp1. Contrary to previous speculation, the TGEV nsp1 structure clearly shows that alpha- and betacoronavirus nsp1s have a common evolutionary origin. However, differences in conservation, shape and surface electrostatics indicate that the mechanism for nsp1-induced suppression of host mRNA translation is likely to be different in the alpha- and betacoronavirus genera.The Modoc virus is a neuroinvasive rodent virus with similar pathology as flavivirus encephalitis in humans. The flaviviral methyltransferase catalyses the two methylations required to complete 5´ mRNA capping, essential for mRNA stability and translation. The structure of the Modoc NS5 methyltransferase domain was determined in complex with its cofactor S-adenosyl-L-methionine. The observed methyltransferase conservation between Modoc and other flaviviral branches, indicates that it may be possible to identify drugs that target a range of flaviviruses and supports the use of Modoc virus as a model for general flaviviral studies.1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) is part of the methylerythritol phosphate (MEP) pathway that produces essential precursors for isoprenoid biosynthesis. This pathway is used by a number of pathogens, including Mycobacterium tuberculosis and Plasmodium falciparum, but it is not present in humans. Using a structure-based approach, we designed a number of MtDXR inhibitors, including a novel fosmidomycin-analogue that exhibited improved activity against P.falciparum in an in vitro blood cell growth assay. The approach also allowed the first design of an inhibitor that bridge both DXR substrate and co-factor binding sites, providing a stepping-stone for further optimization.
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| 3. |
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| 4. |
- Koivula, Anu, et al.
(författare)
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The active site of cellobiohydrolase Cel6A from Trichoderma reesei: the roles of aspartic acids D221 and D175.
- 2002
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Ingår i: J Am Chem Soc. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 124:34, s. 10015-24
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Tidskriftsartikel (refereegranskat)abstract
- Trichoderma reesei cellobiohydrolase Cel6A is an inverting glycosidase. Structural studies have established that the tunnel-shaped active site of Cel6A contains two aspartic acids, D221 and D175, that are close to the glycosidic oxygen of the scissile bond and at hydrogen-bonding distance from each other. Here, site-directed mutagenesis, X-ray crystallography, and enzyme kinetic studies have been used to confirm the role of residue D221 as the catalytic acid. D175 is shown to affect protonation of D221 and to contribute to the electrostatic stabilization of the partial positive charge in the transition state. Structural and modeling studies suggest that the single-displacement mechanism of Cel6A may not directly involve a catalytic base. The value of (D2O)(V) of 1.16 +/- 0.14 for hydrolysis of cellotriose suggests that the large direct effect expected for proton transfer from the nucleophilic water through a water chain (Grotthus mechanism) is offset by an inverse effect arising from reversibly breaking the short, tight hydrogen bond between D221 and D175 before catalysis.
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| 5. |
- Nilsson, Mikael T., et al.
(författare)
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Structural basis for the inhibition of Mycobacterium tuberculosis glutamine synthetase by novel ATP-competitive inhibitors
- 2009
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 393:2, s. 504-513
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Tidskriftsartikel (refereegranskat)abstract
- Glutamine synthetase (GS, EC 6.3.1.2; also known as γ-glutamyl:ammonia ligase) catalyzes the ATP-dependent condensation of glutamate and ammonia to form glutamine. The enzyme has essential roles in different tissues and species, which have led to its consideration as a drug or an herbicide target. In this article, we describe studies aimed at the discovery of new antimicrobial agents targeting Mycobacterium tuberculosis, the causative pathogen of tuberculosis. A number of distinct classes of GS inhibitors with an IC50 of micromolar value or better were identified via high-throughput screening. A commercially available purine analogue similar to one of the clusters identified (the diketopurines), 1-[(3,4-dichlorophenyl)methyl]-3,7-dimethyl-8-morpholin-4-yl-purine-2,6-dione, was also shown to inhibit the enzyme, with a measured IC50 of 2.5 ± 0.4 μM. Two X-ray structures are presented: one is a complex of the enzyme with the purine analogue alone (2.55-Å resolution), and the other includes the compound together with methionine sulfoximine phosphate, magnesium and phosphate (2.2-Å resolution). The former represents a relaxed, inactive conformation of the enzyme, while the latter is a taut, active one. These structures show that the compound binds at the same position in the nucleotide site, regardless of the conformational state. The ATP-binding site of the human enzyme differs substantially, explaining why it has an ∼ 60-fold lower affinity for this compound than the bacterial GS. As part of this work, we devised a new synthetic procedure for generating l-(SR)-methionine sulfoximine phosphate from l-(SR)-methionine sulfoximine, which will facilitate future investigations of novel GS inhibitors.
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| 6. |
- Andaloussi, Mounir, et al.
(författare)
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Design, Synthesis, and X-ray Crystallographic Studies of alpha-Aryl Substituted Fosmidomycin Analogues as Inhibitors of Mycobacterium tuberculosis 1-Deoxy-D-xylulose 5-Phosphate Reductoisomerase
- 2011
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 54:14, s. 4964-4976
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Tidskriftsartikel (refereegranskat)abstract
- The natural antibiotic fosmidomycin acts via inhibition of 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR), an essential enzyme in the non-mevalonate pathway of isoprenoid biosynthesis. Fosmidomycin is active on Mycobacterium tuberculosis DXR (MtDXR), but it lacks antibacterial activity probably because of poor uptake. alpha-Aryl substituted fosmidomycin analogues have more favorable physicochemical properties and are also more active in inhibiting malaria parasite growth. We have solved crystal structures of MtDXR in complex with 3,4-dichlorophenyl substituted fosmidomycin analogues; these show important differences compared to our previously described forsmidomycin-DXR complex. Our best inhibitor has an IC(50) = 0.15 mu M on MtDXR but still lacked activity in a mycobacterial growth assay (MIC > 32 mu g/mL). The combined results, however, provide insights into how DXR accommodates the new inhibitors and serve as an excellent starting point for the design of other novel and more potent inhibitors, particularly against pathogens where uptake is less of a problem, such as the malaria parasite.
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| 7. |
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| 8. |
- Arand, M., et al.
(författare)
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The telltale structures of epoxide hydrolases
- 2003
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Ingår i: Drug metabolism reviews (Softcover ed.). - 0360-2532 .- 1097-9883. ; 35:4, s. 365-383
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Tidskriftsartikel (refereegranskat)abstract
- Traditionally, epoxide hydrolases (EH) have been regarded as xenobiotic-metabolizing enzymes implicated in the detoxification of foreign compounds. They are known to play a key role in the control of potentially genotoxic epoxides that arise during metabolism of many lipophilic compounds. Although this is apparently the main function for the mammalian microsomal epoxide hydrolase (mEH), evidence is now accumulating that the mammalian soluble epoxide hydrolase (sEH), despite its proven role in xenobiotic metabolism, also has a central role in the formation and breakdown of physiological signaling molecules. In addition, a certain class of microbial epoxide hydrolases has recently been identified that is an integral part of a catabolic pathway, allowing the use of specific terpens as sole carbon sources. The recently available x-ray structures of a number of EHs mirror their respective functions: the microbial terpen EH differs in its fold from the canonical α/β hydrolase fold of the xenobiotic-metabolizing mammalian EHs. It appears that the latter fold is the perfect solution for the efficient detoxification of a large variety of structurally different epoxides by a single enzyme, whereas the smaller microbial EH, which has a particularly high turnover number with its prefered substrate, seems to be the better solution for the hydrolysis of one specific substrate. The structure of the sEH also includes an additional catalytic domain that has recently been shown to possess phosphatase activity. Although the physiological substrate for this second active site has not been identified so far, the majority of known phosphatases are involved in signaling processes, suggesting that the sEH phosphatase domain also has a role in the regulation of physiological functions.
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| 9. |
- Björkelid, Christofer, 1980-
(författare)
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Enzymes in the Mycobacterium tuberculosis MEP and CoA Pathways Targeted for Structure-Based Drug Design
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Tuberculosis, caused by the pathogenic bacteria Mycobacterium tuberculosis, is one of the most widespread and deadly infectious diseases today. Treatment of tuberculosis relies on antibiotics that were developed more than 50 years ago. These are now becoming ineffective due to the emergence of antibiotic resistant strains of the bacteria.The aim of the research in this thesis was to develop new antibiotics for tuberculosis treatment. To this end, we targeted enzymes from two essential biosynthetic pathways in M. tuberculosis for drug development. The methylerythritol phosphate (MEP) pathway synthesizes a group of compounds called isoprenoids. These compounds have essential roles in all living organisms. The fact that humans utilize a different pathway for isoprenoid synthesis makes the MEP pathway enzymes attractive targets for drug development. We have determined the structures of two essential enzymes from this pathway by X-ray crystallography: 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR) and 2-C-methyl-D-erythritol 4-phosphate cytidylyltransferase (IspD). These are the first structures of these enzymes from M. tuberculosis. Additionally, structures of the IspD enzyme from the related bacteria Mycobacterium smegmatis were determined. We have characterized these enzymes and evaluated the efficiency of a number of inhibitors of the DXR enzyme by biochemical methods. Crystal structures of DXR in complex with some of these inhibitors were also determined.The second pathway of interest for drug development is the universal pathway for Coenzyme A biosynthesis. Enzymes in this pathway have essential roles in all living organisms. However, the bacterial enzymes have little similarity to the human homologues. We have determined a number of structures of the M. tuberculosis pantothenate kinase (PanK), the regulatory enzyme of this pathway, in complex with two new classes of inhibitory compounds, and evaluated these by biochemical methods.The structures and biochemical characterization of these enzymes provide us with detailed information about their functions and broadens our knowledge of these bacteria. Biochemical and structural information about new inhibitors of these enzymes serve as a starting point for future development of antibiotics against tuberculosis.
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| 10. |
- Björkelid, Christofer, et al.
(författare)
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Structural and biochemical characterization of compounds inhibiting Mycobacterium tuberculosis Pantothenate Kinase
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:25, s. 18260-18270
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Tidskriftsartikel (refereegranskat)abstract
- Mycobacterium tuberculosis, the bacterial causative agent oftuberculosis, currently affects millions of people. The emergence of drug-resistant strains makes development of new antibiotics targeting the bacterium a global health priority. Pantothenate kinase, a key enzyme in the universal biosynthesis of the essential cofactor CoA, was targeted in this study to find new tuberculosis drugs. The biochemicalcharacterizations of two new classes of compounds that inhibitpantothenate kinase from M. tuberculosis are described, along with crystal structures of their enzyme-inhibitor complexes. These represent the first crystal structures of this enzyme with engineered inhibitors. Both classes of compounds bind in the active site of the enzyme, overlapping with the binding sites of the natural substrate and product, pantothenateand phosphopantothenate, respectively. One class of compounds also interferes with binding of the cofactor ATP. The complexes were crystallized in two crystal forms, one of which is in a new space group for this enzyme and diffracts to the highest resolution reported for anypantothenate kinase structure. These two crystal forms allowed, for the first time, modeling of the cofactor-binding loop in both open and closed conformations. The structures also show a binding mode of ATP different from that previously reported for the M. tuberculosis enzyme but similar to that in the pantothenate kinases of other organisms.
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