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 assembly of the polyketide backbone of rifamycin B by the type I rifamycin polyketide synthase, encoded by the rifA-rifE genes, is terminated by the product of the rifF gene, an amide synthase that releases the completed undecaketide as its macrocyclic lactam. The sequence of the RifF protein from Amycolatopsis mediterranei shows 26% identity and 40% homology with the members of the arylamine N-acetyltransferase (NAT) family of proteins. Based on the homology of the primary structures and the similarity of the reactions catalyzed by the two enzymes, we have compared the RifF protein with members of the NAT family. We have modeled the three-dimensional (3D) structure of RifF using NAT from Salmonella typhimurium and Mycobacterium smegmatis as a template. Proteolytic digestions of RifF revealed accessible regions in the protein which are in agreement with the modeled structure. We have expressed the whole protein and individual domains of the protein based on comparison with NAT from S. typhimurium and have purified the proteins by affinity chromatography using a hexahistidine tag. RifF has been further purified using ion-exchange (Mono Q) chromatography. An antiserum has been generated using the C-terminal nona- and tridecapeptides of RifF and has been shown to recognize RifF uniquely. It does not cross-react with any other member of the NAT family.
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PMID:Expression and purification of the rifamycin amide synthase, RifF, an enzyme homologous to the prokaryotic arylamine N-acetyltransferases. 1181 35

Arylamine N-acetyltransferases which acetylate and inactivate isoniazid, an anti-tubercular drug, are found in mycobacteria including Mycobacterium smegmatis and Mycobacterium tuberculosis. We have solved the structure of arylamine N-acetyltransferase from M. smegmatis at a resolution of 1.7 A as a model for the highly homologous NAT from M. tuberculosis. The fold closely resembles that of NAT from Salmonella typhimurium, with a common catalytic triad and domain structure that is similar to certain cysteine proteases. The detailed geometry of the catalytic triad is typical of enzymes which use primary alcohols or thiols as activated nucleophiles. Thermal mobility and structural variations identify parts of NAT which might undergo conformational changes during catalysis. Sequence conservation among eubacterial NATs is restricted to structural residues of the protein core, as well as the active site and a hinge that connects the first two domains of the NAT structure. The structure of M. smegmatis NAT provides a template for modelling the structure of the M. tuberculosis enzyme and for structure-based ligand design as an approach to designing anti-TB drugs.
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PMID:The structure of arylamine N-acetyltransferase from Mycobacterium smegmatis--an enzyme which inactivates the anti-tubercular drug, isoniazid. 1205 3

Mycolic acids represent a major component of the unique cell wall of mycobacteria. Mycolic acid biosynthesis is inhibited by isoniazid, a key frontline antitubercular drug that is inactivated by mycobacterial and human arylamine N-acetyltransferase (NAT). We show that an in-frame deletion of Mycobacterium bovis BCG nat results in delayed entry into log phase, altered morphology, altered cell wall lipid composition, and increased intracellular killing by macrophages. In particular, deletion of nat perturbs biosynthesis of mycolic acids and their derivatives and increases susceptibility of M. bovis BCG to antibiotics that permeate the cell wall. Phenotypic traits are fully complemented by introduction of Mycobacterium tuberculosis nat. We infer from our findings that NAT is critical to normal mycolic acid synthesis and hence other derivative cell wall components and represents a novel target for antituberculosis therapy. In addition, this is the first report of an endogenous role for NAT in mycobacteria.
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PMID:Arylamine N-acetyltransferase is required for synthesis of mycolic acids and complex lipids in Mycobacterium bovis BCG and represents a novel drug target. 1511 74

The gene for NAT (arylamine N-acetyltransferase) from Pseudomonas aeruginosa (panat) has been cloned from genomic DNA, and the gene product (PANAT) expressed as an N-terminal histidine-tagged protein in Escherichia coli and purified via nickel ion affinity chromatography. The specific activities of PANAT against a broad range of substrates have been investigated and compared with those of other prokaryotic NAT enzymes. For most arylamine substrates identified, PANAT exhibits in vitro specific activities typically one order of magnitude greater than those of recombinant NAT enzymes from Mycobacterium smegmatis or Salmonella typhimurium. Among the substrates of PANAT so far identified are the anti-tubercular drug isoniazid, 5-aminosalicylate (a drug used in the treatment of inflammatory bowel disease), as well as important environmental pollutants such as 3,4-dichloroaniline and 2-aminofluorene. As well as acetylating common NAT substrates, PANAT is unique among the prokaryotic NATs so far studied in acetylating the folate precursor 4-aminobenzoic acid and the folate catabolite 4-aminobenzoylglutamate. The recombinant protein has been expressed in sufficient quantity to allow protein crystallization, and we have subsequently determined the 1.95 A structure of PANAT by X-ray crystallography.
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PMID:Expression, purification, characterization and structure of Pseudomonas aeruginosa arylamine N-acetyltransferase. 1544 30

A gene (nat) encoding arylamine N-acetyltransferase (NAT) has been found in Mycobacterium tuberculosis. The gene is expressed and the enzyme is active in growing M. tuberculosis cells. N-Acetyltransferase acetylates and inactivates isoniazid (INH), which is a front-line drug used in tuberculosis (TB) therapy. In this study, it was shown that a previously reported G619A single nucleotide polymorphism (SNP) was conserved in two M. tuberculosis strain families found in the Western Cape Province of South Africa (strain families 3 and 28). Further sequence analysis of isolates in strain family 3 identified a new T529C SNP in NAT resulting in a histidine instead of a tyrosine at position 177. This SNP was found only in isolates from strain family 3, and this mutation affects the highly conserved tyrosine residue close to the active site. Using real-time PCR, the expression of M. tuberculosis nat (tbnat) was determined over a 28 day growth cycle of the M. tuberculosis reference strain (H37Rv). The expression of tbnat occurs early in growth and reaches maximum levels at mid-exponential phase. The exposure of INH-susceptible isolates to low levels of INH resulted in an increase of tbnat expression (reference strain H37Rv, which is wild-type for tbnat, and isolate 1430, containing both SNPs). An INH-resistant isolate (816) exposed to INH showed no change in tbnat expression. The increased expression in the susceptible isolates suggests that INH affects tbnat expression. tbnat may contribute to INH susceptibility, but in combination with other factors.
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PMID:Mutational and expression analysis of tbnat and its response to isoniazid. 1627 33

Mycobacterium bovis BCG and Mycobacterium tuberculosis possess a single arylamine N-acetyltransferase whose gene is predicted to occur within a six-gene operon. Deletion of the nat gene caused an extended lag phase in M. bovis BCG and a cell morphology associated with an altered pattern of cell wall mycolates. Analysis of cDNA from M. bovis BCG shows that during in vitro growth all the genes in the putative nat operon are expressed and the open reading frames are contiguous, supporting the existence of an operon. Two genes in the operon, Mb3599c and Mb3600c, are predicted to encode homologues of enzymes annotated as a 2,3-dihydroxybiphenyl 1,2-dioxygenase (bphC5) and a 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate hydrolase (bphD2), respectively, in Rhodococcus RHA1. As predicted, M. bovis BCG cell lysates metabolized the BphC substrate 2,3-dihydroxybiphenyl (2,3-DHB) to 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA), a BphD substrate, which was subsequently hydrolysed. Immunoprecipitation of the BphD homologue from these lysates led to an accumulation of HOPDA. M. bovis BCG growth on both solid and liquid media was inhibited with either 2,3-DHB or an inhibitor of BphC, 3-chlorocatechol (3-CC). In addition, incubation with 2,3-DHB affects the lipid composition of the cell wall resulting in a diminished level of mycolates and an altered cell morphology similar to the Deltanat strain. We propose the enzymes encoded by the putative operon have a similar endogenous role to that of the NAT enzyme and are part of a pathway important for cell wall synthesis.
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PMID:Characterization of the putative operon containing arylamine N-acetyltransferase (nat) in Mycobacterium bovis BCG. 1635 27

The arylamine N-acetyltransferase (NAT) enzymes have been found in a broad range of both eukaryotic and prokaryotic organisms. The NAT enzymes catalyse the transfer of an acetyl group from acetyl Co-enzyme A onto the terminal nitrogen of a range of arylamine, hydrazine and arylhydrazine compounds. Recently, several NAT structures have been reported from different prokaryotic sources including Salmonella typhimurium, Mycobacterium smegmatis and Pseudomonas aeruginosa. Bioinformatics analysis of the Mesorhizobium loti genome revealed two NAT paralogues, the first example of multiple NAT isoenzymes in a eubacterial organism. The M. loti NAT 1 enzyme was recombinantly expressed and purified for X-ray crystallographic studies. The purified enzyme was crystallized in 0.5 M Ca(OAc)2, 16% PEG 3350, 0.1 M Tris-HCl pH 8.5 using the sitting-drop vapour-diffusion method. A data set diffracting to 2.0 A was collected from a single crystal at 100 K. The crystal belongs to the orthorhombic spacegroup P2(1)2(1)2(1), with unit-cell parameters a = 53.2, b = 97.3, c = 114.3 A. The structure was refined to a final free-R factor of 24.8%. The structure reveals that despite low sequence homology, M. loti NAT1 shares the common fold as reported in previous NAT structures and exhibits the same catalytic triad of residues (Cys-His-Asp) in the active site.
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PMID:Structure of Mesorhizobium loti arylamine N-acetyltransferase 1. 1650 79

A computational study was performed to better understand the differences between human arylamine N-acetyltransferase (NAT) 1 and 2. Homology models were constructed from available crystal structures, and comparisons of the active site residues 125, 127, and 129 for these two enzymes provide insight into observed substrate differences. The NAT2 model provided a basis for understanding how some of the common polymorphisms may affect the structure of this protein. Molecular dynamics simulations of the human NAT models and the template structure (NAT from Mycobacterium smegmatis) were performed and showed the models to be stable and reasonable. Docking studies of hydroxylated heterocyclic amines in the models of NAT1 and NAT2 probed the differences exhibited by these two proteins with mutagenic agents. The hydroxylated heterocyclic amines were only able to fit into the NAT2 active site, and an alternative binding site by the phosphate-binding loop was found using our models and will be discussed. Quantum mechanical calculations on the O-acetylation reaction of the hydroxylated heterocyclic amines N-OH MeIQx and N-OH PhIP show that the reaction coordinates differ for these two compounds, but the activation barrier separating the reactant from the product are both low. The results of this study suggest that common polymorphisms in human NAT2 are distant from the active site and are more likely to destabilize the enzyme than affect catalysis. Additionally, the quantum mechanical calculations show that the observed differences in mutagenic activity between N-OH MeIQx and N-OH PhIP are not related to their acetylation reaction with NAT.
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PMID:Insights into the o-acetylation reaction of hydroxylated heterocyclic amines by human arylamine N-acetyltransferases: a computational study. 1697 22

In this study, we show that extracts and a purified compound of Warburgia salutaris exhibit anti-mycobacterial activity against Mycobacterium tuberculosis H37Rv and Mycobacterium bovis BCG Pasteur. The extracts did not inhibit growth of Escherichia coli and were not toxic to cultured mammalian macrophage cells at the concentrations at which anti-mycobacterial activity was observed. The extract and pure compound inhibited pure recombinant arylamine N-acetyltransferase (NAT), an enzyme involved in mycobacterial cell wall lipid synthesis. Moreover, neither extract nor pure compound inhibited growth of a strain of M. bovis BCG in which nat has been deleted suggesting that NAT may indeed be a target within the mycobacterial cell. The purified compound is a novel drimane sesquiterpenoid lactone, 11alpha-hydroxycinnamosmolide. These studies show that W. salutaris is a useful source of anti-tubercular compounds for further analysis and supports the hypothesis of a link between NAT inhibition and anti-mycobacterial activity.
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PMID:Inhibition of mycobacterial arylamine N-acetyltransferase contributes to anti-mycobacterial activity of Warburgia salutaris. 1736 35

In Mycobacterium tuberculosis, the genes hsaD (2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid hydrolase) and nat (arylamine N-acetyltransferase) are essential for survival inside of host macrophages. These genes act as an operon and have been suggested to be involved in cholesterol metabolism. However, the role of NAT in this catabolic pathway has not been determined. In an effort to better understand the function of these proteins, we have expressed, purified and characterized TBNAT (NAT from M. tuberculosis) and HsaD (2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid hydrolase) from M. tuberculosis. Both proteins demonstrated remarkable heat stability with TBNAT and HsaD retaining >95% of their activity after incubation at 60 degrees C for 30 min. The first and second domains of TBNAT were demonstrated to be very important to the heat stability of the protein, as the transfer of these domains caused a dramatic reduction in the heat stability. The specific activity of TBNAT was tested against a broad range of acyl-CoA cofactors using hydralazine as a substrate. TBNAT was found to be able to utilize not just acetyl-CoA, but also n-propionyl-CoA and acetoacetyl-CoA, although at a lower rate. As propionyl-CoA is a product of cholesterol catabolism, we propose that NAT could have a role in the utilization of this important cofactor.
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PMID:Temperature stability of proteins essential for the intracellular survival of Mycobacterium tuberculosis. 1901 50


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