Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026918 (Mycobacterium)
 52,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cyclic AMP receptor protein (CRP, also called catabolite gene activator protein or CAP) plays a key role in metabolic regulation in bacteria and has become a widely studied model allosteric transcription factor. On binding its effector cAMP in the N-terminal domain, CRP undergoes a structural transition to a conformation capable of specific DNA binding in the C-terminal domain and transcription initiation. The crystal structures of Escherichia coli CRP (EcCRP) in the cAMP-bound state, both with and without DNA, are known, although its structure in the off state (cAMP-free, apoCRP) remains unknown. We describe the crystal structure at 2.0A resolution of the cAMP-free CRP homodimer from Mycobacterium tuberculosis H(37)R(v) (MtbCRP), whose sequence is 30% identical with EcCRP, as the first reported structure of an off-state CRP. The overall structure is similar to that seen for the cAMP-bound EcCRP, but the apo MtbCRP homodimer displays a unique level of asymmetry, with a root mean square deviation of 3.5A between all Calpha positions in the two subunits. Unlike structures of on-state EcCRP and other homologs in which the C-domains are asymmetrically positioned but possess the same internal conformation, the two C-domains of apo MtbCRP differ both in hinge structure and in internal arrangement, with numerous residues that have completely different local environments and hydrogen bond interactions, especially in the hinge and DNA-binding regions. Comparison of the structures of apo MtbCRP and DNA-bound EcCRP shows how DNA binding would be inhibited in the absence of cAMP and supports a mechanism involving functional asymmetry in apoCRP.
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PMID:Profound asymmetry in the structure of the cAMP-free cAMP Receptor Protein (CRP) from Mycobacterium tuberculosis. 1919 43

B lymphocytes play an important role in the immune response induced by mucosal adjuvants. In this study we investigated the in vitro antigen-presenting cell (APC) properties of human B cells upon treatment with cholera toxin (CT) and Escherichia coli heat-labile enterotoxin (LT) and nontoxic counterparts of these toxins, such as the B subunit of CT (CT-B) and the mutant of LT lacking ADP ribosyltransferase activity (LTK63). Furthermore, forskolin (FSK), a direct activator of adenylate cyclase, and cyclic AMP (cAMP) analogues were used to investigate the role of the increase in intracellular cAMP caused by the A subunit of CT and LT. B lymphocytes were cultured with adjuvants and polyclonal stimuli necessary for activation of B cells in the absence of CD4 T cells. Data indicated that treatment with CT, LT, FSK, or cAMP analogues, but not treatment with CT-B or LTK63, upregulated surface activation markers on B cells, such as CD86 and HLA-DR, and induced inhibition of the proliferation of B cells at early time points, while it increased cell death in long-term cultures. Importantly, B cells treated with CT, LT, or FSK were able to induce pronounced proliferation of both CD4(+) and CD8(+) allogeneic T cells compared with untreated B cells and B cells treated with CT-B and LTK63. Finally, only treatment with toxins or FSK induced antigen-specific T-cell proliferation in Mycobacterium tuberculosis purified protein derivative or tetanus toxoid responder donors. Taken together, these results indicated that the in vitro effects of CT and LT on human B cells are mediated by cAMP.
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PMID:Cholera toxin and Escherichia coli heat-labile enterotoxin, but not their nontoxic counterparts, improve the antigen-presenting cell function of human B lymphocytes. 1922 74

Mycolic acids are major and specific lipids of Mycobacterium tuberculosis cell envelope. Their synthesis requires the condensation by Pks13 of a C(22)-C(26) fatty acid with the C(50)-C(60) meromycolic acid activated by FadD32, a fatty acyl-AMP ligase essential for mycobacterial growth. A combination of biochemical and enzymatic approaches demonstrated that FadD32 exhibits substrate specificity for relatively long-chain fatty acids. More importantly, FadD32 catalyzes the transfer of the synthesized acyl-adenylate onto specific thioester acceptors, thus revealing the protein acyl-ACP ligase function. Therefore, FadD32 might be the prototype of a group of M. tuberculosis polyketide-synthase-associated adenylation enzymes possessing such activity. A substrate analog of FadD32 inhibited not only the enzyme activity but also mycolic acid synthesis and mycobacterial growth, opening an avenue for the development of novel antimycobacterial agents.
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PMID:The dual function of the Mycobacterium tuberculosis FadD32 required for mycolic acid biosynthesis. 1947 15

With 8.9 million new cases and 1.7 million deaths per year, tuberculosis is a leading global killer that has not been effectively controlled. The causative agent, Mycobacterium tuberculosis, proliferates within host macrophages where it modifies both its intracellular and local tissue environment, resulting in caseous granulomas with incomplete bacterial sterilization. Although infection by various mycobacterial species produces a cyclic AMP burst within macrophages that influences cell signalling, the underlying mechanism for the cAMP burst remains unclear. Here we show that among the 17 adenylate cyclase genes present in M. tuberculosis, at least one (Rv0386) is required for virulence. Furthermore, we demonstrate that the Rv0386 adenylate cyclase facilitates delivery of bacterial-derived cAMP into the macrophage cytoplasm. Loss of Rv0386 and the intramacrophage cAMP it delivers results in reductions in TNF-alpha production via the protein kinase A and cAMP response-element-binding protein pathway, decreased immunopathology in animal tissues, and diminished bacterial survival. Direct intoxication of host cells by bacterial-derived cAMP may enable M. tuberculosis to modify both its intracellular and tissue environments to facilitate its long-term survival.
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PMID:Cyclic AMP intoxication of macrophages by a Mycobacterium tuberculosis adenylate cyclase. 1951 56

We show that Cibacron Blue F3GA dye resin chromatography can be used to identify ligands that specifically interact with proteins from Mycobacterium tuberculosis, and that the identification of these ligands can facilitate structure determination by enhancing the quality of crystals. Four native Mtb proteins of the aldehyde dehydrogenase (ALDH) family were previously shown to be specifically eluted from a Cibacron Blue F3GA dye resin with nucleosides. In this study we characterized the nucleoside-binding specificity of one of these ALDH isozymes (recombinant Mtb Rv0223c) and compared these biochemical results with co-crystallization experiments with different Rv0223c-nucleoside pairings. We found that the strongly interacting ligands (NAD and NADH) aided formation of high-quality crystals, permitting solution of the first Mtb ALDH (Rv0223c) structure. Other nucleoside ligands (AMP, FAD, adenosine, GTP and NADP) exhibited weaker binding to Rv0223c, and produced co-crystals diffracting to lower resolution. Difference electron density maps based on crystals of Rv0223c with various nucleoside ligands show most share the binding site where the natural ligand NAD binds. From the high degree of similarity of sequence and structure compared to human mitochondrial ALDH-2 (BLAST Z-score = 53.5 and RMSD = 1.5 A), Rv0223c appears to belong to the ALDH-2 class. An altered oligomerization domain in the Rv0223c structure seems to keep this protein as monomer whereas native human ALDH-2 is a multimer.
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PMID:Analysis of nucleoside-binding proteins by ligand-specific elution from dye resin: application to Mycobacterium tuberculosis aldehyde dehydrogenases. 1991 9

The pathogen Mycobacterium tuberculosis produces a burst of cAMP upon infection of macrophages. Bacterial cyclic AMP receptor proteins (CRP) are transcription factors that respond to cAMP by binding at target promoters when cAMP concentrations increase. Rv3676 (CRP(Mt)) is a CRP family protein that regulates expression of genes (rpfA and whiB1) that are potentially involved in M. tuberculosis persistence and/or emergence from the dormant state. Here, the CRP(Mt) homodimer is shown to bind two molecules of cAMP (one per protomer) at noninteracting sites. Furthermore, cAMP binding by CRP(Mt) was relatively weak, entropy driven, and resulted in a relatively small enhancement in DNA binding. Tandem CRP(Mt)-binding sites (CRP1 at -58.5 and CRP2 at -37.5) were identified at the whiB1 promoter (PwhiB1). In vitro transcription reactions showed that CRP1 is an activating site and that CRP2, which was only occupied in the presence of cAMP or at high CRP(Mt) concentrations in the absence of cAMP, is a repressing site. Binding of CRP(Mt) to CRP1 was not essential for open complex formation but was required for transcription activation. Thus, these data suggest that binding of CRP(Mt) to the PwhiB1 CRP1 site activates transcription at a step after open complex formation. In contrast, high cAMP concentrations allowed occupation of both CRP1 and CRP2 sites, resulting in inhibition of open complex formation. Thus, M. tuberculosis CRP has evolved several distinct characteristics, compared with the Escherichia coli CRP paradigm, to allow it to regulate gene expression against a background of high concentrations of cAMP.
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PMID:Mycobacterium tuberculosis cAMP receptor protein (Rv3676) differs from the Escherichia coli paradigm in its cAMP binding and DNA binding properties and transcription activation properties. 2002 78

The cutR gene was identified 314 bp upstream of the divergently oriented cutB1C1A1 operon encoding carbon monoxide (CO) dehydrogenase in Mycobacterium sp. strain JC1. Its deduced product was composed of 320 amino acid residues with a calculated molecular mass of 34.1 kDa and exhibits a basal sequence similarity to the regulatory proteins belonging to the LysR family. Using a cutR deletion mutant, it was demonstrated that CutR is required for the efficient utilization of CO by Mycobacterium sp. strain JC1 growing with CO as the sole source of carbon and energy. CutR served as a transcriptional activator for expression of the duplicated cutBCA operons (cutB1C1A1 and cutB2C2A2) and was involved in the induction of the cutBCA operons by CO. The cutBCA operons were also subjected to catabolite repression. An inverted repeat sequence (TGTGA-N(6)-TCACA) with a perfect match with the binding motif of cyclic AMP receptor protein was identified immediately upstream of and overlapping with the translational start codons of cutB1 and cutB2. This palindrome sequence was shown to be involved in catabolite repression of the cutBCA operons. The transcription start point of cutR was determined to be the nucleotide G located 36 bp upstream of the start codon of cutR. Expression of cutR was higher in Mycobacterium sp. strain JC1 grown with glucose than that grown with CO.
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PMID:Identification of trans- and cis-control elements involved in regulation of the carbon monoxide dehydrogenase genes in Mycobacterium sp. strain JC1 DSM 3803. 2051 3

Phthiocerol and phthiodiolone dimycocerosates (DIMs) and phenolic glycolipids (PGLs) are complex lipids located at the cell surface of Mycobacterium tuberculosis that play a key role in the pathogenicity of tuberculosis. Most of the genes involved in the biosynthesis of these compounds are clustered on a region of the M. tuberculosis chromosome, the so-called DIM + PGL locus. Among these genes, four ORFs encode FadD proteins, which activate and transfer biosynthetic intermediates onto various polyketide synthases that catalyze the formation of these lipids. In this study, we investigated the roles of FadD22, FadD26 and FadD29 in the biosynthesis of DIMs and related compounds. Biochemical characterization of the lipids produced by a spontaneous Mycobacterium bovis BCG mutant harboring a large deletion within fadD26 revealed that FadD26 is required for the production of DIMs but not of PGLs. Additionally, using allelic exchange recombination, we generated an unmarked M. tuberculosis mutant containing a deletion within fadD29. Biochemical analyses of this strain revealed that, like fadD22, this gene encodes a protein that is specifically involved in the biosynthesis of PGLs, indicating that both FadD22 and FadD29 are responsible for one particular reaction in the PGL biosynthetic pathway. These findings were also supported by in vitro enzymatic studies showing that these enzymes have different properties, FadD22 displaying a p-hydroxybenzoyl-AMP ligase activity, and FadD29 a fatty acyl-AMP ligase activity. Altogether, these data allowed us to precisely define the functions fulfilled by the various FadD proteins encoded by the DIM + PGL cluster.
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PMID:Delineation of the roles of FadD22, FadD26 and FadD29 in the biosynthesis of phthiocerol dimycocerosates and related compounds in Mycobacterium tuberculosis. 2055 5

Activation of the pro-drug isoniazid (INH) as an anti-tubercular drug in Mycobacterium tuberculosis involves its conversion to isonicotinyl-NAD, a reaction that requires the catalase-peroxidase KatG. This report shows that the reaction proceeds in the absence of KatG at a slow rate in a mixture of INH, NAD(+), Mn(2+), and O(2), and that the inclusion of KatG increases the rate by >7 times. Superoxide, generated by either Mn(2+)- or KatG-catalyzed reduction of O(2), is an essential intermediate in the reaction. Elimination of the peroxidatic process by mutation slows the rate of reaction by 60% revealing that the peroxidatic process enhances, but is not essential for isonicotinyl-NAD formation. The isonicotinyl-NAD(*+) radical is identified as a reaction intermediate, and its reduction by superoxide is proposed. Binding sites for INH and its co-substrate, NAD(+), are identified for the first time in crystal complexes of Burkholderia pseudomallei catalase-peroxidase with INH and NAD(+) grown by co-crystallization. The best defined INH binding sites were identified, one in each subunit, on the opposite side of the protein from the entrance to the heme cavity in a funnel-shaped channel. The NAD(+) binding site is approximately 20 A from the entrance to the heme cavity and involves interactions primarily with the AMP portion of the molecule in agreement with the NMR saturation transfer difference results.
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PMID:Isonicotinic acid hydrazide conversion to Isonicotinyl-NAD by catalase-peroxidases. 2055 37

Gamma interferon (IFN-gamma) is a crucial cytokine for protection against Mycobacterium tuberculosis, but the mechanism of IFN-gamma transcription is still unclear. The cyclic AMP (cAMP) responsive element binding (CREB) proteins belong to the bZip (basic leucine zipper) family of transcription factors and are essential for T-cell function and cytokine production. This study focused on the capacity of CREB proteins to regulate IFN-gamma transcription in CD3(+) T cells obtained from tuberculosis (TB) patients and persons with latent tuberculosis infection (LTBI) in China. The electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), and Western blotting were used to demonstrate the regulatory role of CREB. EMSA (in vitro) and ChIP (in vivo) experiments suggested CREB could bind to the IFN-gamma proximal promoter in persons with LTBI, whereas no binding was detected in TB patients. Western blotting confirmed the expression of CREB proteins, especially serine-133-phosphorylated CREB, was markedly reduced in TB patients compared with persons with LTBI. These results suggested that CREB could promote the transcription and production of IFN-gamma through binding with the IFN-gamma proximal promoter, but the regulatory role of CREB was decreased in tuberculosis patients owing to diminished expression of CREB proteins, which in turn reduced the IFN-gamma production.
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PMID:CREB is a positive transcriptional regulator of gamma interferon in latent but not active tuberculosis infections. 2068 39


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