GliP, a multimodular nonribosomal peptide synthetase in Aspergillus fumigatus, makes the diketopiperazine scaffold of gliotoxin.
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.
Balibar
Carl J
CJ
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
Walsh
Christopher T
CT
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
D054659:Diketopiperazines; D005656:Fungal Proteins; D010879:Piperazines; D005912:Gliotoxin; D010453:Peptide Synthases