title: Sequential Inactivation of Gliotoxin by the S-Methyltransferase TmtA.
abstract: The epipolythiodioxopiperazine (ETP) gliotoxin mediates toxicity via its reactive thiol groups and thereby contributes to virulence of the human pathogenic fungus Aspergillus fumigatus. Self-intoxication of the mold is prevented either by reversible oxidation of reduced gliotoxin or by irreversible conversion to bis(methylthio)gliotoxin. The latter is produced by the S-methyltransferase TmtA and attenuates ETP biosynthesis. Here, we report the crystal structure of TmtA in complex with S-(5'-adenosyl)-l-homocysteine. TmtA features one substrate and one cofactor binding pocket per protein, and thus, bis-thiomethylation of gliotoxin occurs sequentially. Molecular docking of substrates and products into the active site of TmtA reveals that gliotoxin forms specific interactions with the protein surroundings, and free energy calculations indicate that methylation of the C10a-SH group precedes alkylation of the C3-SH site. Altogether, TmtA is well suited to selectively convert gliotoxin and to control its biosynthesis, suggesting that homologous enzymes serve to regulate the production of their toxic natural sulfur compounds in a similar manner.
authors.affiliation: Center for Integrated Protein Science Munich (CIPSM) at the Department Chemie, Technische Universität München , Lichtenbergstr. 4, 85748 Garching, Germany.
authors.forename: Elke R
authors.initials: ER
authors.lastname: Duell
authors.affiliation: Center for Integrated Protein Science Munich (CIPSM) at the Department Chemie, Technische Universität München , Lichtenbergstr. 4, 85748 Garching, Germany.
authors.forename: Manuel
authors.initials: M
authors.lastname: Glaser
authors.affiliation: Center for Integrated Protein Science Munich (CIPSM) at the Department Chemie, Technische Universität München , Lichtenbergstr. 4, 85748 Garching, Germany.
authors.forename: Camille
authors.initials: C
authors.lastname: Le Chapelain
authors.affiliation: Center for Integrated Protein Science Munich (CIPSM) at the Department Chemie, Technische Universität München , Lichtenbergstr. 4, 85748 Garching, Germany.
authors.forename: Iris
authors.initials: I
authors.lastname: Antes
authors.affiliation: Center for Integrated Protein Science Munich (CIPSM) at the Department Chemie, Technische Universität München , Lichtenbergstr. 4, 85748 Garching, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Groll
authors.affiliation: Center for Integrated Protein Science Munich (CIPSM) at the Department Chemie, Technische Universität München , Lichtenbergstr. 4, 85748 Garching, Germany.
authors.forename: Eva M
authors.initials: EM
authors.lastname: Huber
mesh_terms: D005912:Gliotoxin / Q000037:antagonists & inhibitors*; D006801:Humans; D008780:Methyltransferases / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular
chemical_list: D005912:Gliotoxin; D008780:Methyltransferases