title: GliP, a multimodular nonribosomal peptide synthetase in Aspergillus fumigatus, makes the diketopiperazine scaffold of gliotoxin.
abstract: The fungal metabolite gliotoxin has a redox-active disulfide bridge spanning carbons 3 and 6 of a diketopiperazine (DKP) scaffold. The proposed DKP synthetase, GliP, from Aspergillus fumigatus Af293, is a three module (A1-T1-C1-A2-T2-C2-T3) 236 kDa protein that can be overproduced in soluble form in Escherichia coli. Once primed on its three thiolation domains with phosphopantetheine prosthetic groups, GliP activates and tethers l-Phe on T1 and l-Ser on T2, before generating the l-Phe-l-Ser-S-T2 dipeptidyl enzyme intermediate. Release of the dipeptide as the cyclic DKP happens slowly both in wild-type GliP and in enzyme forms where C2 and T3 have been mutationally inactivated. The lack of a thioesterase domain in GliP may account both for the slow release and for the directed fate of intramolecular cyclization to create the DKP scaffold for subsequent elaboration to gliotoxin.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Balibar
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D001232:Aspergillus fumigatus / Q000201:enzymology* / Q000235:genetics; D054659:Diketopiperazines; D004789:Enzyme Activation / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005912:Gliotoxin / Q000096:biosynthesis* / Q000737:chemistry; D009154:Mutation; D010453:Peptide Synthases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010879:Piperazines / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics
chemical_list: D054659:Diketopiperazines; D005656:Fungal Proteins; D010879:Piperazines; D005912:Gliotoxin; D010453:Peptide Synthases