Nejvíce citovaný článek - PubMed ID 21998585
Dormant cells of Mycobacterium tuberculosis, in addition to low metabolic activity and a high level of drug resistance, are characterized by 'non-culturability'-a specific reversible state of the inability of the cells to grow on solid media. The biochemical characterization of this physiological state of the pathogen is only superficial, pending clarification of the metabolic processes that may exist in such cells. In this study, applying LC-MS proteomic profiling, we report the analysis of proteins accumulated in dormant, 'non-culturable' M. tuberculosis cells in an in vitro model of self-acidification of mycobacteria in the post-stationary phase, simulating the in vivo persistence conditions-the raw data are available via ProteomeXchange with identifier PXD028849. This approach revealed the preservation of 1379 proteins in cells after 5 months of storage in dormancy; among them, 468 proteins were statistically different from those in the actively growing cells and bore a positive fold change (FC). Differential analysis revealed the proteins of the pH-dependent regulatory system PhoP and allowed the reconstruction of the reactions of central carbon/glycerol metabolism, as well as revealing the salvaged pathways of mycothiol and UMP biosynthesis, establishing the cohort of survival enzymes of dormancy. The annotated pathways mirror the adaptation of the mycobacterial metabolic machinery to life within lipid-rich macrophages: especially the involvement of the methyl citrate and glyoxylate pathways. Thus, the current in vitro model of M. tuberculosis self-acidification reflects the biochemical adaptation of these bacteria to persistence in vivo. Comparative analysis with published proteins displaying antigenic properties makes it possible to distinguish immunoreactive proteins among the proteins bearing a positive FC in dormancy, which may include specific antigens of latent tuberculosis. Additionally, the biotransformatory enzymes (oxidoreductases and hydrolases) capable of prodrug activation and stored up in the dormant state were annotated. These findings may potentially lead to the discovery of immunodiagnostic tests for early latent tuberculosis and trigger the discovery of efficient drugs/prodrugs with potency against non-replicating, dormant populations of mycobacteria.
Mycobacterium tuberculosis (MTb), the causative agent of tuberculosis, can persist in macrophages for decades, maintaining its basic metabolic activities. Phosphoenolpyruvate carboxykinase (Pck; EC 4.1.1.32) is a key player in central carbon metabolism regulation. In replicating MTb, Pck is associated with gluconeogenesis, but in non-replicating MTb, it also catalyzes the reverse anaplerotic reaction. Here, we explored the role of selected cysteine residues in function of MTb Pck under different redox conditions. Using mass spectrometry analysis we confirmed formation of S-S bridge between cysteines C391 and C397 localized in the C-terminal subdomain. Molecular dynamics simulations of C391-C397 bridged model indicated local conformation changes needed for formation of the disulfide. Further, we used circular dichroism and Raman spectroscopy to analyze the influence of C391 and C397 mutations on Pck secondary and tertiary structures, and on enzyme activity and specificity. We demonstrate the regulatory role of C391 and C397 that form the S-S bridge and in the reduced form stabilize Pck tertiary structure and conformation for gluconeogenic and anaplerotic reactions.
- MeSH
- aminokyselinové motivy MeSH
- biokatalýza * MeSH
- cystein metabolismus MeSH
- disulfidy metabolismus MeSH
- fosfoenolpyruvátkarboxykinasa (závislá na ATP) chemie metabolismus MeSH
- kinetika MeSH
- molekulární modely MeSH
- mutace genetika MeSH
- mutageneze cílená MeSH
- mutantní proteiny chemie MeSH
- Mycobacterium tuberculosis enzymologie MeSH
- sekundární struktura proteinů MeSH
- sekvence aminokyselin MeSH
- stabilita enzymů MeSH
- substrátová specifita MeSH
- tandemová hmotnostní spektrometrie MeSH
- terciární struktura proteinů MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- cystein MeSH
- disulfidy MeSH
- fosfoenolpyruvátkarboxykinasa (závislá na ATP) MeSH
- mutantní proteiny MeSH
Tuberculosis, the second leading infectious disease killer after HIV, remains a top public health priority. The causative agent of tuberculosis, Mycobacterium tuberculosis (Mtb), which can cause both acute and clinically latent infections, reprograms metabolism in response to the host niche. Phosphoenolpyruvate carboxykinase (Pck) is the enzyme at the center of the phosphoenolpyruvate-pyruvate-oxaloacetate node, which is involved in regulating the carbon flow distribution to catabolism, anabolism, or respiration in different states of Mtb infection. Under standard growth conditions, Mtb Pck is associated with gluconeogenesis and catalyzes the metal-dependent formation of phosphoenolpyruvate. In non-replicating Mtb, Pck can catalyze anaplerotic biosynthesis of oxaloacetate. Here, we present insights into the regulation of Mtb Pck activity by divalent cations. Through analysis of the X-ray structure of Pck-GDP and Pck-GDP-Mn2+ complexes, mutational analysis of the GDP binding site, and quantum mechanical (QM)-based analysis, we explored the structural determinants of efficient Mtb Pck catalysis. We demonstrate that Mtb Pck requires presence of Mn2+ and Mg2+ cations for efficient catalysis of gluconeogenic and anaplerotic reactions. The anaplerotic reaction, which preferably functions in reducing conditions that are characteristic for slowed or stopped Mtb replication, is also effectively activated by Fe2+ in the presence of Mn2+ or Mg2+ cations. In contrast, simultaneous presence of Fe2+ and Mn2+ or Mg2+ inhibits the gluconeogenic reaction. These results suggest that inorganic ions can contribute to regulation of central carbon metabolism by influencing the activity of Pck. Furthermore, the X-ray structure determination, biochemical characterization, and QM analysis of Pck mutants confirmed the important role of the Phe triad for proper binding of the GDP-Mn2+ complex in the nucleotide binding site and efficient catalysis of the anaplerotic reaction.
- MeSH
- aktivace enzymů MeSH
- fosfoenolpyruvátkarboxykinasa (závislá na ATP) chemie genetika metabolismus MeSH
- glukoneogeneze MeSH
- katalýza MeSH
- kationty dvojmocné MeSH
- kineze MeSH
- konformace proteinů MeSH
- lidé MeSH
- molekulární modely MeSH
- molekulární sekvence - údaje MeSH
- multimerizace proteinu MeSH
- mutace MeSH
- Mycobacterium tuberculosis enzymologie genetika MeSH
- nukleotidy metabolismus MeSH
- sekvence aminokyselin MeSH
- sekvenční seřazení MeSH
- vazebná místa MeSH
- vodíková vazba MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- fosfoenolpyruvátkarboxykinasa (závislá na ATP) MeSH
- kationty dvojmocné MeSH
- nukleotidy MeSH
Tuberculosis remains a major health concern worldwide. Eradication of its causative agent, the bacterial pathogen Mycobacterium tuberculosis, is particularly challenging due to a vast reservoir of latent carriers of the disease. Despite the misleading terminology of a so-called dormant state associated with latent infections, the bacteria have to maintain basic metabolic activities. Hypoxic conditions have been widely used as an in vitro system to study this dormancy. Such studies identified a rearrangement of central carbon metabolism to exploit fermentative processes caused by the lack of oxygen. Phosphoenolpyruvate carboxykinase (Pck; EC 4.1.1.32) is the enzyme at the center of these metabolic rearrangements. Although Pck is associated with gluconeogenesis under standard growth conditions, the enzyme can catalyze the reverse reaction, supporting anaplerosis of the tricarboxylic acid cycle, under conditions leading to slowed or stopped bacterial replication. To study the mechanisms that regulate the switch between two Pck functions, we systematically investigated factors influencing the gluconeogenic and anaplerotic reaction kinetics. We demonstrate that a reducing environment, as found under hypoxia-triggered non-replicating conditions, accelerates the reaction in the anaplerotic direction. Furthermore, we identified proteins that interact with Pck. The interaction between Pck and the reduced form of mycobacterial thioredoxin, gene expression of which is increased under hypoxic conditions, also increased the Pck anaplerotic activity. We thus propose that a reducing environment and the protein-protein interaction with thioredoxin in particular enable the Pck anaplerotic function under fermentative growth conditions.
- Klíčová slova
- Enzyme Kinetics, Hypoxia, Metabolism, Mycobacterium Tuberculosis, Oxidation-Reduction, Phosphoenolpyruvate Carboxykinase, Thioredoxin,
- MeSH
- bakteriální proteiny genetika metabolismus MeSH
- citrátový cyklus fyziologie MeSH
- fosfoenolpyruvátkarboxykinasa (závislá na ATP) genetika metabolismus MeSH
- Mycobacterium tuberculosis enzymologie genetika MeSH
- oxidace-redukce MeSH
- regulace genové exprese enzymů fyziologie MeSH
- regulace genové exprese u bakterií fyziologie MeSH
- thioredoxiny genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- bakteriální proteiny MeSH
- fosfoenolpyruvátkarboxykinasa (závislá na ATP) MeSH
- thioredoxiny MeSH
A potential novel fumarate reductase gene designated frd1A was isolated by screening a marine metagenomic library through a sequence-based strategy. Sequence analyses indicated that Frd1A and other putative fumarate reductases were closely related. The putative fumarate reductase gene was subcloned into a pETBlue-2 vector and expressed in Escherichia coli Tuner(DE3)pLacІ cells. The recombinant protein was purified to homogeneity. Functional characterization by high-performance liquid chromatography demonstrated that the recombinant Frd1A protein could catalyze the hydrogenation of fumarate to succinate acid. The Frd1A protein displayed an optimal activity at pH 7.0 and 28 °C, which could be stimulated by adding metal ions such as Zn(2+) and Mg(2+). The Frd1A enzyme showed a comparable affinity and catalytic efficiency under optimal reaction conditions: k m =0.227 mmol/L, v max= 29.9 U/mg, and k cat/k m=5.44 × 10(4) per mol/s. The identification of Frd1A protein underscores the potential of marine metagenome screening for novel biomolecules.
- MeSH
- aktivátory enzymů metabolismus MeSH
- Escherichia coli genetika MeSH
- exprese genu MeSH
- fumaráty metabolismus MeSH
- fylogeneze MeSH
- hořčík metabolismus MeSH
- kinetika MeSH
- klonování DNA MeSH
- koncentrace vodíkových iontů MeSH
- kyselina jantarová metabolismus MeSH
- metagenom * MeSH
- molekulární sekvence - údaje MeSH
- oxidace-redukce MeSH
- rekombinantní proteiny genetika metabolismus MeSH
- sekvenční analýza DNA MeSH
- sekvenční homologie aminokyselin MeSH
- stabilita enzymů MeSH
- sukcinátdehydrogenasa chemie genetika metabolismus MeSH
- teplota MeSH
- vodní organismy MeSH
- vysokoúčinná kapalinová chromatografie MeSH
- zinek metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- aktivátory enzymů MeSH
- fumaráty MeSH
- hořčík MeSH
- kyselina jantarová MeSH
- rekombinantní proteiny MeSH
- sukcinátdehydrogenasa MeSH
- zinek MeSH
