Source:http://linkedlifedata.com/resource/pubmed/id/19663400
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rdf:type | |
lifeskim:mentions |
umls-concept:C0023689,
umls-concept:C0030685,
umls-concept:C0056801,
umls-concept:C0220781,
umls-concept:C0376315,
umls-concept:C0391871,
umls-concept:C0680255,
umls-concept:C1265395,
umls-concept:C1283071,
umls-concept:C1514562,
umls-concept:C1880022,
umls-concept:C1880389,
umls-concept:C1883204,
umls-concept:C1883221,
umls-concept:C1963578
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pubmed:issue |
36
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pubmed:dateCreated |
2009-9-8
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pubmed:abstractText |
The fungal neurotoxin alpha-cyclopiazonic acid (CPA), a nanomolar inhibitor of Ca2+-ATPase, has a pentacyclic indole tetramic acid scaffold that arises from one molecule of tryptophan, acetyl-CoA, malonyl-CoA, and dimethylallyl pyrophosphate by consecutive action of three enzymes, CpaS, CpaD, and CpaO. CpaS is a hybrid, two module polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) that makes and releases cyclo-acetoacetyl-L-tryptophan (cAATrp), the tetramic acid that serves as substrate for subsequent prenylation and oxidative cyclization to the five ring CPA scaffold. The NRPS module in CpaS has a predicted four-domain organization of condensation, adenylation, thiolation, and reductase* (C-A-T-R*), where R* lacks the critical Ser-Tyr-Lys catalytic triad of the short chain dehydrogenase/reductase (SDR) superfamily. By heterologous overproduction in Escherichia coli of the 56 kDa Aspergillus flavus CpaS TR* didomain and the single T and R* domains, we demonstrate that CpaS catalyzes a Dieckmann-type cyclization on the N-acetoacetyl-Trp intermediate bound in thioester linkage to the phosphopantetheinyl arm of the T domain to form and release cAATrp. This occurs without any participation of NAD(P)H, so R* does not function as a canonical SDR family member. Use of the T and R* domains in in trans assays enabled multiple turnovers and evaluation of specific mutants. Mutation of the D3803 residue in the R* domain, conserved in other fungal tetramate synthetases, abolished activity both in in trans and in cis (TR*) activity assays. It is likely that cyclization of beta-ketoacylaminoacyl-S-pantetheinyl intermediates to released tetramates represents a default cyclization/release route for redox-incompetent R* domains embedded in NRPS assembly lines.
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pubmed:grant | |
pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Indoles,
http://linkedlifedata.com/resource/pubmed/chemical/Mycotoxins,
http://linkedlifedata.com/resource/pubmed/chemical/Oxidoreductases,
http://linkedlifedata.com/resource/pubmed/chemical/Tryptophan,
http://linkedlifedata.com/resource/pubmed/chemical/cyclopiazonic acid
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pubmed:status |
MEDLINE
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pubmed:month |
Sep
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pubmed:issn |
1520-4995
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pubmed:author | |
pubmed:issnType |
Electronic
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pubmed:day |
15
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pubmed:volume |
48
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
8746-57
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pubmed:dateRevised |
2010-9-16
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pubmed:meshHeading | |
pubmed:year |
2009
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pubmed:articleTitle |
Cyclopiazonic acid biosynthesis in Aspergillus sp.: characterization of a reductase-like R* domain in cyclopiazonate synthetase that forms and releases cyclo-acetoacetyl-L-tryptophan.
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pubmed:affiliation |
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't,
Research Support, N.I.H., Extramural
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