| Structural highlights
Function
GLIT_ASPFU Thioredoxin reductase; part of the gene cluster that mediates the biosynthesis of gliotoxin, a member of the epipolythiodioxopiperazine (ETP) class of toxins characterized by a disulfide bridged cyclic dipeptide (PubMed:15979823, PubMed:21612254). The first step in gliotoxin biosynthesis is the condensation of serine and phenylalanine to form the cyclo-L-phenylalanyl-L-serine diketopiperazine (DKP) by the NRPS gliP (PubMed:17154540, PubMed:21612254). GliP is also able to produce the DKP cyclo-L-tryptophanyl-L-serine, suggesting that the substrate specificity of the first adenylation (A) domain in gliP is sufficiently relaxed to accommodate both L-Phe and L-Trp (PubMed:23434416). The cytochrome P450 monooxygenase gliC has been shown to catalyze the subsequent hydroxylation of the alpha-carbon of L-Phe in cyclo-L-phenylalanyl-L-serine whereas the second cytochrome P450 enzyme, gliF, is presumably involved in the modification of the DKP side chain (PubMed:24039048, PubMed:23434416). The glutathione S-transferase (GST) gliG then forms a bis-glutathionylated biosynthetic intermediate which is responsible for the sulfurization of gliotoxin (PubMed:21513890, PubMed:21749092). This bis-glutathionylated intermediate is subsequently processed by the gamma-glutamyl cyclotransferase gliK to remove both gamma-glutamyl moieties (PubMed:22903976, PubMed:24039048). Subsequent processing via gliI yields a biosynthetic intermediate, which is N-methylated via the N-methyltransferase gliN, before the gliotoxin oxidoreductase gliT-mediated disulfide bridge closure (PubMed:20548963, PubMed:22936680, PubMed:24039048, PubMed:25062268). GliN-mediated amide methylation confers stability to ETP, damping the spontaneous formation of tri- and tetrasulfides (PubMed:25062268). Intracellular dithiol gliotoxin oxidized by gliT is subsequently effluxed by gliA (PubMed:26150413). GliT is required for self-protection against gliotoxin (PubMed:20548963, PubMed:26150413). GliT plays a role in preventing dysregulation of the methyl/methionine cycle to control intracellular S-adenosylmethionine (SAM) depletion and S-adenosylhomocysteine (SAH) homeostasis during gliotoxin biosynthesis and exposure (PubMed:26150413).[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
Publication Abstract from PubMed
Nature provides a rich source of compounds with diverse chemical structures and biological activities, among them, sulfur-containing metabolites from bacteria and fungi. Some of these compounds bear a disulfide moiety that is indispensable for their bioactivity. Specialized oxidoreductases such as GliT, HlmI, and DepH catalyze the formation of this disulfide bridge in the virulence factor gliotoxin, the antibiotic holomycin, and the anticancer drug romidepsin, respectively. We have examined all three enzymes by X-ray crystallography and activity assays. Despite their differently sized substrate binding clefts and hence, their diverse substrate preferences, a unifying reaction mechanism is proposed based on the obtained crystal structures and further supported by mutagenesis experiments.
Flavoenzyme-catalyzed formation of disulfide bonds in natural products.,Scharf DH, Groll M, Habel A, Heinekamp T, Hertweck C, Brakhage AA, Huber EM Angew Chem Int Ed Engl. 2014 Feb 17;53(8):2221-4. doi: 10.1002/anie.201309302., Epub 2014 Jan 20. PMID:24446392[12]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Balibar CJ, Walsh CT. GliP, a multimodular nonribosomal peptide synthetase in Aspergillus fumigatus, makes the diketopiperazine scaffold of gliotoxin. Biochemistry. 2006 Dec 19;45(50):15029-38. PMID:17154540 doi:http://dx.doi.org/10.1021/bi061845b
- ↑ Schrettl M, Carberry S, Kavanagh K, Haas H, Jones GW, O'Brien J, Nolan A, Stephens J, Fenelon O, Doyle S. Self-protection against gliotoxin--a component of the gliotoxin biosynthetic cluster, GliT, completely protects Aspergillus fumigatus against exogenous gliotoxin. PLoS Pathog. 2010 Jun 10;6(6):e1000952. doi: 10.1371/journal.ppat.1000952. PMID:20548963 doi:http://dx.doi.org/10.1371/journal.ppat.1000952
- ↑ Davis C, Carberry S, Schrettl M, Singh I, Stephens JC, Barry SM, Kavanagh K, Challis GL, Brougham D, Doyle S. The role of glutathione S-transferase GliG in gliotoxin biosynthesis in Aspergillus fumigatus. Chem Biol. 2011 Apr 22;18(4):542-52. doi: 10.1016/j.chembiol.2010.12.022. PMID:21513890 doi:http://dx.doi.org/10.1016/j.chembiol.2010.12.022
- ↑ Forseth RR, Fox EM, Chung D, Howlett BJ, Keller NP, Schroeder FC. Identification of cryptic products of the gliotoxin gene cluster using NMR-based comparative metabolomics and a model for gliotoxin biosynthesis. J Am Chem Soc. 2011 Jun 29;133(25):9678-81. doi: 10.1021/ja2029987. Epub 2011 Jun, 6. PMID:21612254 doi:http://dx.doi.org/10.1021/ja2029987
- ↑ Scharf DH, Remme N, Habel A, Chankhamjon P, Scherlach K, Heinekamp T, Hortschansky P, Brakhage AA, Hertweck C. A dedicated glutathione S-transferase mediates carbon-sulfur bond formation in gliotoxin biosynthesis. J Am Chem Soc. 2011 Aug 17;133(32):12322-5. doi: 10.1021/ja201311d. Epub 2011 Jul, 22. PMID:21749092 doi:http://dx.doi.org/10.1021/ja201311d
- ↑ Gallagher L, Owens RA, Dolan SK, O'Keeffe G, Schrettl M, Kavanagh K, Jones GW, Doyle S. The Aspergillus fumigatus protein GliK protects against oxidative stress and is essential for gliotoxin biosynthesis. Eukaryot Cell. 2012 Oct;11(10):1226-38. doi: 10.1128/EC.00113-12. Epub 2012 Aug, 17. PMID:22903976 doi:http://dx.doi.org/10.1128/EC.00113-12
- ↑ Scharf DH, Chankhamjon P, Scherlach K, Heinekamp T, Roth M, Brakhage AA, Hertweck C. Epidithiol formation by an unprecedented twin carbon-sulfur lyase in the gliotoxin pathway. Angew Chem Int Ed Engl. 2012 Oct 1;51(40):10064-8. doi: 10.1002/anie.201205041., Epub 2012 Aug 31. PMID:22936680 doi:http://dx.doi.org/10.1002/anie.201205041
- ↑ Chang SL, Chiang YM, Yeh HH, Wu TK, Wang CC. Reconstitution of the early steps of gliotoxin biosynthesis in Aspergillus nidulans reveals the role of the monooxygenase GliC. Bioorg Med Chem Lett. 2013 Apr 1;23(7):2155-7. doi: 10.1016/j.bmcl.2013.01.099., Epub 2013 Feb 4. PMID:23434416 doi:http://dx.doi.org/10.1016/j.bmcl.2013.01.099
- ↑ Scharf DH, Chankhamjon P, Scherlach K, Heinekamp T, Willing K, Brakhage AA, Hertweck C. Epidithiodiketopiperazine biosynthesis: a four-enzyme cascade converts glutathione conjugates into transannular disulfide bridges. Angew Chem Int Ed Engl. 2013 Oct 11;52(42):11092-5. doi: 10.1002/anie.201305059. , Epub 2013 Aug 26. PMID:24039048 doi:http://dx.doi.org/10.1002/anie.201305059
- ↑ Scharf DH, Habel A, Heinekamp T, Brakhage AA, Hertweck C. Opposed effects of enzymatic gliotoxin N- and S-methylations. J Am Chem Soc. 2014 Aug 20;136(33):11674-9. doi: 10.1021/ja5033106. Epub 2014 Aug, 7. PMID:25062268 doi:http://dx.doi.org/10.1021/ja5033106
- ↑ Owens RA, O'Keeffe G, Smith EB, Dolan SK, Hammel S, Sheridan KJ, Fitzpatrick DA, Keane TM, Jones GW, Doyle S. Interplay between Gliotoxin Resistance, Secretion, and the Methyl/Methionine Cycle in Aspergillus fumigatus. Eukaryot Cell. 2015 Sep;14(9):941-57. doi: 10.1128/EC.00055-15. Epub 2015 Jul 6. PMID:26150413 doi:http://dx.doi.org/10.1128/EC.00055-15
- ↑ Scharf DH, Groll M, Habel A, Heinekamp T, Hertweck C, Brakhage AA, Huber EM. Flavoenzyme-catalyzed formation of disulfide bonds in natural products. Angew Chem Int Ed Engl. 2014 Feb 17;53(8):2221-4. doi: 10.1002/anie.201309302., Epub 2014 Jan 20. PMID:24446392 doi:http://dx.doi.org/10.1002/anie.201309302
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