Crystal Structure of Imidazole Glycerol Phosphate Synthase

Chaudhuri, Barnali N.; Lange, Stephanie C.; Myers, Rebecca S.; Chittur, Sridar V.; Davisson, V. Jo; Smith, Janet L.

doi:10.1016/s0969-2126(01)00661-x

Cited by 101 publications

(87 citation statements)

References 39 publications

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“…The barrel exhibits a twofold repeat arrangement, (␤␣) [1][2][3][4] and (␤␣) [5][6][7][8] , with two symmetrically related helical insertions between ␤1 and a1 and between ␤5 and ␣5 (Fig. 1b) that suggest this ␤-barrel protein may have evolved by gene duplication similar to what has been suggested for the barrel structures of HisA and HisF (24).…”

Section: Resultsmentioning

confidence: 88%

“…Channeling processes are particularly advantageous over the free diffusion of reaction products through the bulk solvent because they can protect chemically labile intermediates from breakdown, prevent loss of nonpolar intermediates by diffusion across cell membranes, or protect the cell from toxic intermediates. Crystallographic studies on a number of different enzyme systems involved in substrate channeling (3)(4)(5)(6)(7)(8)(9)(10)(11) have revealed important structural factors that mediate intersubunit or interdomain communication and facilitate the efficient transfer of intermediates between distant active sites.…”

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confidence: 99%

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Crystal structure of a bifunctional aldolase–dehydrogenase: Sequestering a reactive and volatile intermediate

Manjasetty

Powlowski

Vrielink

2003

Proc. Natl. Acad. Sci. U.S.A.

137

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The crystal structure of the bifunctional enzyme 4-hydroxy-2-ketovalerate aldolase (DmpG)͞acylating acetaldehyde dehydrogenase (DmpF), which is involved in the bacterial degradation of toxic aromatic compounds, has been determined by multiwavelength anomalous dispersion (MAD) techniques and refined to 1.7-Å resolution. Structures of the two polypeptides represent a previously unrecognized subclass of metal-dependent aldolases, and of a CoA-dependent dehydrogenase. The structure reveals a mixed state of NAD ؉ binding to the DmpF protomer. Domain movements associated with cofactor binding in the DmpF protomer may be correlated with channeling and activity at the DmpG protomer. In the presence of NAD ؉ a 29-Å-long sequestered tunnel links the two active sites. Two barriers are visible along the tunnel and suggest control points for the movement of the reactive and volatile acetaldehyde intermediate between the two active sites. E nzymatic channeling is a process by which intermediates are moved directly between active sites in a sequential reaction pathway without equilibrating with the bulk phase (1, 2). Channeling processes are particularly advantageous over the free diffusion of reaction products through the bulk solvent because they can protect chemically labile intermediates from breakdown, prevent loss of nonpolar intermediates by diffusion across cell membranes, or protect the cell from toxic intermediates. Crystallographic studies on a number of different enzyme systems involved in substrate channeling (3-11) have revealed important structural factors that mediate intersubunit or interdomain communication and facilitate the efficient transfer of intermediates between distant active sites.A bifunctional aldolase-dehydrogenase catalyzes the final two steps of the meta-cleavage pathway for catechol, an intermediate in many bacterial species in the degradation of phenols, toluates, naphthalene, biphenyls and other aromatic compounds (reviewed in ref. 12). Thus, 4-hydroxy-2-ketovalerate aldolase (DmpG; EC 4.1.3.-) and acetaldehyde dehydrogenase (acylating) (DmpF; EC 1.2.1.10) from a methylphenol-degrading pseudomonad convert 4-hydroxy-2-ketovalerate to pyruvate and acetyl-CoA by way of the intermediate acetaldehyde (Scheme 1).The two enzymes are tightly associated with each other (13,14). Whereas the aldolase appears to be inactive when expressed without the dehydrogenase, the dehydrogenase retains some activity when expressed in the absence of aldolase (14), suggesting that at least the dehydrogenase active site is distinct from that of the aldolase. Several lines of evidence are consistent with channeling of acetaldehyde between the active sites. For example, the conversion of 4-hydroxy-2-ketovalerate to acetyl-CoA occurs Ϸ20 times faster than that of acetaldehyde to acetyl-CoA, and the K m for acetaldehyde exceeds 50 mM, a physiologically irrelevant concentration (J.P., unpublished data). In addition, it has been shown that the aldolase activity is stimulated by the addition of the dehydrogenase cofactor to t...

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Section: Resultsmentioning

confidence: 88%

mentioning

confidence: 99%

Crystal structure of a bifunctional aldolase–dehydrogenase: Sequestering a reactive and volatile intermediate

Manjasetty

Powlowski

Vrielink

2003

Proc. Natl. Acad. Sci. U.S.A.

137

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“…Tryptophan synthase from S. typhimurium (58,59), thymidylate synthase/dihydrofolate reductase (TS-DHFR) from Leishmania major (48,60), glutamate synthase from Synechocystis sp. (61), and imidazole glycerol-phosphate synthase from yeast (62,63) are very well characterized examples of bifunctional enzymes that exhibit both channeling and interdomain communications. Domaindomain interactions in these enzymes become evident upon formation of substrate-enzyme complexes (or reaction intermediates) at either of the two reaction centers, which reciprocally and allosterically activate turnover at the other reaction center.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Bifunctional γ-Glutamate-cysteine Ligase/Glutathione Synthetase (GshF) of Pasteurella multocida

Vergauwen

Vos

Beeumen

2006

Journal of Biological Chemistry

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Glutamate-cysteine ligase (␥-ECL) and glutathione synthetase (GS) are the two unrelated ligases that constitute the glutathione biosynthesis pathway in most eukaryotes, purple bacteria, and cyanobacteria. ␥-ECL is a member of the glutamine synthetase family, whereas GS enzymes group together with highly diverse carboxylto-amine/thiol ligases, all characterized by the so-called two-domain ATP-grasp fold. This generalized scheme toward the formation of glutathione, however, is incomplete, as functional steadystate levels of intracellular glutathione may also accumulate solely by import, as has been reported for the Pasteurellaceae member Haemophilus influenzae, as well as for certain Gram-positive enterococci and streptococci, or by the action of a bifunctional fusion protein (termed GshF), as has been reported recently for the Gram-positive firmicutes Streptococcus agalactiae and Listeria monocytogenes. Here, we show that yet another member of the Pasteurellaceae family, Pasteurella multocida, acquires glutathione both by import and GshF-driven biosynthesis. Domain architecture analysis shows that this P. multocida GshF bifunctional ligase contains an N-terminal ␥-proteobacterial ␥-ECL-like domain followed by a typical ATP-grasp domain, which most closely resembles that of cyanophycin synthetases, although it has no significant homology with known GS ligases. Recombinant P. multocida GshF overexpresses as an ϳ85-kDa protein, which, on the basis of gel-sizing chromatography, forms dimers in solution. The ␥-ECL activity of GshF is regulated by an allosteric type of glutathione feedback inhibition (K i ‫؍‬ 13.6 mM). Furthermore, steady-state kinetics, on the basis of which we present a novel variant of half-of-the-sites reactivity, indicate intimate domain-domain interactions, which may explain the bifunctionality of GshF proteins.Glutathione (GSH; L-␥-glutamyl-L-cysteinylglycine) is the predominant low molecular weight peptide thiol present in many Gram-negative bacteria and in virtually all eukaryotes, except those that lack mitochondria (1, 2). Glutathione is made in a highly conserved two-step ATP-dependent biosynthesis pathway by two unrelated peptide bondforming enzymes (3). In the first and rate-limiting reaction, ␥-glutamate-cysteine ligase (␥-ECL) 2 (EC 6.3.2.2) condenses the ␥-carboxylate of L-glutamic acid with L-cysteine to form the dipeptide ␥-glutamylcys-where Me 2ϩ can be magnesium or manganese (4, 5). In the second step, ␥-EC is condensed with glycine in a reaction catalyzed by glutathione synthetase (GS; EC 6.3.2.3), according towhere Me 2ϩ again can be magnesium or manganese. The activity of eukaryotic ␥-ECL is precisely controlled by nonallosteric glutathione feedback inhibition, the limited availability of cellular L-Cys, and the transcriptional and posttranslational regulation of the expression and activity of the enzyme under various physiological conditions (6). Bacterial glutathione homeostasis is less well characterized, although glutathione feedback inhibition appears to be of major importa...

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“…Thermal Stabilization-Structures of several enzymes of the histidine biosynthesis pathway from the hyperthermophile T. maritima have already been determined, including tmHisA (23), tmHisF (23), tmHisH (24), the binary tmHisH-tmHisF complex (24), and the hetero-octameric tmHisG-tmHisZ complex, 2 thereby allowing comparisons with the respective enzyme structures from mesophilic organisms (25)(26)(27)(28). Previous statistical analyses of large structural data sets revealed that the frequency of salt bridges, surface polarity, and structural compactness may be important criteria that affect the structural parameters for thermal stabilization, in general (29,30), and in T. maritima, in particular (31,32).…”

Section: Discussionmentioning

confidence: 99%

Structural Studies of the Catalytic Reaction Pathway of a Hyperthermophilic Histidinol-phosphate Aminotransferase

Fernández

Vega

Lehmann

et al. 2004

Journal of Biological Chemistry

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In histidine biosynthesis, histidinol-phosphate aminotransferase catalyzes the transfer of the amino group from glutamate to imidazole acetol-phosphate producing 2-oxoglutarate and histidinol phosphate. In some organisms such as the hyperthermophile Thermotoga maritima, specific tyrosine and aromatic amino acid transaminases have not been identified to date, suggesting an additional role for histidinol-phosphate aminotransferase in other transamination reactions generating aromatic amino acids. To gain insight into the specific function of this transaminase, we have determined its crystal structure in the absence of any ligand except phosphate, in the presence of covalently bound pyridoxal 5 -phosphate, of the coenzyme histidinol phosphate adduct, and of pyridoxamine 5 -phosphate. The enzyme accepts histidinol phosphate, tyrosine, tryptophan, and phenylalanine, but not histidine, as substrates. The structures provide a model of how these different substrates could be accommodated by histidinol-phosphate aminotransferase. Some of the structural features of the enzyme are more preserved between the T. maritima enzyme and a related threonine-phosphate decarboxylase from S. typhimurium than with histidinol-phosphate aminotransferases from different organisms.

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Crystal Structure of Imidazole Glycerol Phosphate Synthase

Cited by 101 publications

References 39 publications

Crystal structure of a bifunctional aldolase–dehydrogenase: Sequestering a reactive and volatile intermediate

Crystal structure of a bifunctional aldolase–dehydrogenase: Sequestering a reactive and volatile intermediate

Characterization of the Bifunctional γ-Glutamate-cysteine Ligase/Glutathione Synthetase (GshF) of Pasteurella multocida

Structural Studies of the Catalytic Reaction Pathway of a Hyperthermophilic Histidinol-phosphate Aminotransferase

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