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Found 1 structure.
Displayed structure 1
| L-Cys2Ac-(1-2)-a-D-GlcpN-(1-3)-L-myoIno | Show graphically |
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Structure type: monomer
Trivial name: mycothiol
Compound class: glycoside
Contained glycoepitopes: IEDB_141807,IEDB_151531
Low-molecular-weight (LMW) thiols are extensively involved in the maintenance of cellular redox potentials and the protection of cells from a variety of reactive chemical and electrophilic species. However, we recently found that the metabolic coupling of two LMW thiols - mycothiol (MSH) and ergothioneine (EGT) - programs the biosynthesis of the anti-infective agent lincomycin A. Remarkably, such a constructive role of the thiols in the biosynthesis of natural products has so far received relatively little attention. We speculate that the unusual thiol EGT might function as a chiral thiolation carrier (for modification) and a novel activator (for glycosylation) of sugar. Additionally, we examine recent evidence for LMW thiols (MSH and others) as sulfur donors of sulfur-containing natural products. Clearly, the LMW thiols have more diverse activities beyond cell protection, and more attention should be paid to the correlation of their functions with thiol-dependent enzymes
ergothioneine, low-molecular-weight thiols, mycothiol, non-Leloir pathway, sulfur incorporation, thiolation carrier
NCBI PubMed ID: 26515639Low-molecular-mass thiols in organisms are well known for their redox-relevant role in protection against various endogenous and exogenous stresses. In eukaryotes and Gram-negative bacteria, the primary thiol is glutathione (GSH), a cysteinyl-containing tripeptide. In contrast, mycothiol (MSH), a cysteinyl pseudo-disaccharide, is dominant in Gram-positive actinobacteria, including antibiotic-producing actinomycetes and pathogenic mycobacteria. MSH is equivalent to GSH, either as a cofactor or as a substrate, in numerous biochemical processes, most of which have not been characterized, largely due to the dearth of information concerning MSH-dependent proteins. Actinomycetes are able to produce another thiol, ergothioneine (EGT), a histidine betaine derivative that is widely assimilated by plants and animals for variable physiological activities. The involvement of EGT in enzymatic reactions, however, lacks any precedent. Here we report that the unprecedented coupling of two bacterial thiols, MSH and EGT, has a constructive role in the biosynthesis of lincomycin A, a sulfur-containing lincosamide (C8 sugar) antibiotic that has been widely used for half a century to treat Gram-positive bacterial infections. EGT acts as a carrier to template the molecular assembly, and MSH is the sulfur donor for lincomycin maturation after thiol exchange. These thiols function through two unusual S-glycosylations that program lincosamide transfer, activation and modification, providing the first paradigm for EGT-associated biochemical processes and for the poorly understood MSH-dependent biotransformations, a newly described model that is potentially common in the incorporation of sulfur, an element essential for life and ubiquitous in living systems
biosynthesis, lincomycin A, S-glycoside, mycothiols
NCBI PubMed ID: 25607359Actinobacteria such as Mycobacterium tuberculosis use the unique thiol mycothiol (MSH) as their primary reducing agent and in the detoxification of xenobiotics. N-Acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside deacetylase (MshB) is the metal-dependent deacetylase that catalyzes the deacetylation of N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside, the committed step in MSH biosynthesis. We previously used docking studies to identify specific side chains that may contribute as molecular determinants of MshB substrate specificity [Huang, X., and Hernick, M. (2014) Biopolymers 101, 406-417]. Herein, we probe the molecular basis of N-acetylglucosamine (GlcNAc) recognition and turnover by MshB using a combination of site-directed mutagenesis and kinetic studies (mutants examined, L19A, E47A, R68A, D95A, M98A, D146N, and F216A). Results from these studies indicate that MshB is unable to catalyze the turnover of GlcNAc upon loss of the Arg68 or Asp95 side chains, consistent with the proposal that these side chains make critical hydrogen bonding interactions with substrate. The activity of the D146N mutant is ~10-fold higher than that of the D146A mutant, suggesting that the ability to accept a hydrogen bond at this position contributes to GlcNAc substrate specificity. Because there does not appear to be a direct contact between Asp146 and substrate, this effect is likely mediated via positioning of other catalytically important residues. Finally, we probed side chains located on mobile loops and in a hydrophobic cavity and identified two additional side chains (Met98 and Glu47) that contribute to GlcNAc recognition and turnover by MshB. Together, results from these studies confirm some of the molecular determinants of GlcNAc substrate specificity by MshB, which should aid the development of MshB inhibitors
Mycobacterium tuberculosis, mycothiol, MshB
NCBI PubMed ID: 26024468Mycothiol serves as the primary reducing agent in Mycobacterium species, and is also a cofactor for the detoxification of xenobiotics. Mycothiol conjugate amidase (Mca) is a metalloamidase that catalyzes the cleavage of MS-conjugates to form a mercapturic acid, which is excreted from the mycobacterium, and 1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside. Herein we report on the metal cofactor preferences of Mca from Mycobacterium smegmatis and Mycobacterium tuberculosis. Importantly, results from homology models of Mca from M. smegmatis and M. tuberculosis suggest that the metal binding site of Mca is identical to that of the closely related protein N-acetyl-1-D-myo-inosityl-2-amino-2-deoxy-α-D-glucopyranoside deacetylase (MshB). This finding is supported by results from zinc ion affinity measurements that indicate Mca and MshB have comparable K(D)(ZnII) values (~10-20 pM). Furthermore, results from pull-down experiments using Halo-Mca indicate that Mca purifies with (stoichiometric) Fe2+ when purified under anaerobic conditions, and Zn2+ when purified under aerobic conditions. Consequently, Mca is likely a Fe2+-dependent enzyme under physiological conditions; with Zn2+-Mca an experimental artifact that could become biologically relevant under oxidatively stressed conditions. Importantly, these findings suggest that efforts towards the design of Mca inhibitors should include targeting the Fe2+ form of the enzyme
iron, mycothiol, MshB, mycothiol conjugate amidase, metalloamidase, zinc
NCBI PubMed ID: 26044118Thiol compounds with low-molecular weight, such as glutathione, mycothiol (MSH), bacillithiol, and ergothioneine (ERG), are known to protect microorganisms from oxidative stresses. Mycobacteria and actinobacteria utilize both MSH and ERG. The biological functions of MSH in mycobacteria have been extensively studied by genetic and biochemical studies, which have suggested it has critical roles for detoxification in cells. In contrast, the biological functions of ERG remain ambiguous because its biosynthetic genes were only recently identified in Mycobacterium avium. In this study, we constructed mutants of Streptomyces coelicolor A3(2), in which either the MSH or ERG biosynthetic gene was disrupted, and examined their phenotypes. A mshC (SCO1663)-disruptant completely lost MSH productivity. In contrast, a disruptant of the egtA gene (SCO0910) encoding γ-glutamyl-cysteine synthetase unexpectedly retained reduced productivity of ERG, probably because of the use of l-cysteine instead of γ-glutamyl-cysteine. Both disruptants showed delayed growth at the late logarithmic phase and were more susceptible to hydrogen peroxide and cumene hydroperoxide than the parental strain. Interestingly, the ERG-disruptant, which still kept reduced ERG productivity, was more susceptible. Furthermore, the ERG-disruptant accumulated 5-fold more MSH than the parental strain. In contrast, the amount of ERG was almost the same between the MSH-disruptant and the parental strain. Taken together, our results suggest that ERG is more important than MSH in S. coelicolor A3(2)
oxidative stress, ergothioneine, mycothiol, biological function, Streptomyces coelicolor
NCBI PubMed ID: 25683449Drug-resistant Mycobacterium tuberculosis is a growing health problem. As proof of principle that the bacterial-specific metabolite mycothiol could be used as a delivery agent for antimycobacterial agents, simplified analogues of mycothiol were synthesised containing an S-trichloroethenyl substituted cysteine residue. It was envisaged that uptake of the mycothiol analogue would be followed by release of the known cytotoxin S-trichloroethenyl cysteine by the action of mycothiol S-conjugate amidase or its paralog, mycothiol deacetylase MshB. Promising activity was displayed against model Mycobacteria, although further development will be required to improve selectivity
antibacterial, antimycobacterial, mycothiol, prodrug, trichlorovinyl cysteine
NCBI PubMed ID: 25881831Methionine sulfoxide reductases are conserved enzymes that reduce oxidized methionines in proteins and play a pivotal role in cellular redox signaling. We have unraveled the redox relay mechanisms of methionine sulfoxide reductase A of the pathogen Corynebacterium diphtheriae (Cd-MsrA) and shown that this enzyme is coupled to two independent redox relay pathways. Steady-state kinetics combined with mass spectrometry of Cd-MsrA mutants give a view of the essential cysteine residues for catalysis. Cd-MsrA combines a nucleophilic cysteine sulfenylation reaction with an intramolecular disulfide bond cascade linked to the thioredoxin pathway. Within this cascade, the oxidative equivalents are transferred to the surface of the protein while releasing the reduced substrate. Alternatively, MsrA catalyzes methionine sulfoxide reduction linked to the mycothiol/mycoredoxin-1 pathway. After the nucleophilic cysteine sulfenylation reaction, MsrA forms a mixed disulfide with mycothiol, which is transferred via a thiol disulfide relay mechanism to a second cysteine for reduction by mycoredoxin-1. With x-ray crystallography, we visualize two essential intermediates of the thioredoxin relay mechanism and a cacodylate molecule mimicking the substrate interactions in the active site. The interplay of both redox pathways in redox signaling regulation forms the basis for further research into the oxidative stress response of this pathogen
kinetics, X-ray crystallography, enzyme mechanism, disulfide, oxidation-reduction (redox), redox, redox regulation, thiol, thiol-disulfide exchange
NCBI PubMed ID: 25752606| New query | Export IDs | Home | Help |
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