The structure and configuration of pseudomonic acid C

Clayton, J. P.; O’Hanlon, Peter J.; Rogers, Norman H.

doi:10.1016/s0040-4039(00)71533-4

Cited by 39 publications

(21 citation statements)

References 8 publications

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“…The other main compo--nents are pseudomonic acid B (2, PA--B, 8%) which has an additional hydroxyl group at C8, 6 and pseudomonic acid C (3, PA--C, < 2%) which has a double bond in place of the epoxide group at C10--C11. 7 PA--D (1, 4'--5'--alkene) has also been reported as a very minor component. Simple biosyn--thetic logic would suggest that PA--A is formed by epoxi--dation of the 10,11--double bond in PA--C 3, and PA--B 2, by a further hydroxylation of PA--A at C8.…”

Section: Introductionmentioning

confidence: 99%

Biosynthesis of Mupirocin by Pseudomonas fluorescens NCIMB 10586 Involves Parallel Pathways

Gao

Hothersall

et al. 2014

J. Am. Chem. Soc.

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Detailed metabolic profiling of mutant strains produced by systematic inactivation of PKS and tailoring genes, along with re--feeding of isolated metabo--lites to mutant stains, has allowed the isolation of a large number of novel metabolites, identification of the 10,11--epoxidase and the full characterisation of the mupirocin biosynthetic pathway which proceeds via major (10,11--epoxide) and minor (10,11--alkene) parallel pathways.

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Section: Introductionmentioning

confidence: 99%

Biosynthesis of Mupirocin by Pseudomonas fluorescens NCIMB 10586 Involves Parallel Pathways

Gao

Hothersall

et al. 2014

J. Am. Chem. Soc.

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“…It is a competitive inhibitor of isoleucyl-tRNA synthetase (IleRS), blocking binding of isoleucine and ATP to IleRS (1). Mupirocin is a mixture of pseudomonic acids (PA) 5 produced by Pseudomonas fluorescens NCIMB 10586, with PA-A accounting for 90%. PA-A consists of a C 9 saturated fatty acid (9-hydroxynonanoic acid, 9HN) joined via an ester linkage to a C 17 unsaturated polyketide moiety containing a tetrahydropyran ring (monic acid, MA, Fig.…”

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confidence: 99%

“…1A) (2,3). PA-B has an additional hydroxyl group at C-8 (4), in PA-C the C-10,11 epoxide group is replaced with a double bond (5), and PA-D has an additional double bond at C-4Ј,5Ј in the 9-HN moiety (6). Polyketides are biosynthesized by condensation of small carboxylic acids catalyzed by ketosynthases (KS) generating ␤-carbonyl groups that may then be left unreduced or reduced partially or fully by the combined activities of ketoreductases (KR), dehydratases (DH), and enoyl reductases (ER).…”

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confidence: 99%

Mutational Analysis Reveals That All Tailoring Region Genes Are Required for Production of Polyketide Antibiotic Mupirocin by Pseudomonas fluorescens

Hothersall

Rahman

et al. 2007

Journal of Biological Chemistry

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The Pseudomonas fluorescens mupirocin biosynthetic cluster encodes six proteins involved in polyketide biosynthesis and 26 single polypeptides proposed to perform largely tailoring functions. In-frame deletions in the tailoring open reading frames demonstrated that all are required for mupirocin production. A bidirectional promoter region was identified between mupF, which runs counter to other open reading frames and its immediate neighbor macpC, implying the 74-kb cluster consists of two transcriptional units. mupD/E and mupJ/K must be cotranscribed as pairs for normal function implying co-assembly during translation. MupJ and K belong to a widely distributed enzyme pair implicated, with MupH, in methyl addition. Deletion of mupF, a putative ketoreductase, produced a mupirocin analogue with a C-7 ketone. Deletion of mupC, a putative dienoyl CoA reductase, generated an analogue whose structure indicated that MupC is also implicated in control of the oxidation state around the tetrahydropyran ring of monic acid. Double mutants with ⌬mupC and ⌬mupO, ⌬mupU, ⌬mupV, or ⌬macpE produced pseudomonic acid B but not pseudomonic acid A, as do the mupO, U, V, and macpE mutants, indicating that MupC must work after MupO, U, and V.

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“…[6][7][8] The passivity was suggested from the observed deprotonation of hydrated chromium hydroxide layer and subsequent formation of a chromium oxide barrier layer, and by the reduced adsorption of chloride in the presence of absorbed molybdate. In the latter case, MoO 4 2Ϫ has been shown to form a cation selective layer on SS exposed to solutions of neutral to acidic pH.…”

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confidence: 99%

A Duplex Mechanism-Based Model for the Interaction Between Chromate Ions and the Hydrated Oxide Film on Aluminum Alloys

Chidambaram

Clayton

Halada

2003

J. Electrochem. Soc.

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In order to understand more clearly the nature of the anodic film formed on aluminum and its alloys, and the mechanism of inhibition of corrosion by chromates, a novel investigation has been made on the anodic film formed on AA1060 using X-ray photoelectron spectroscopy. The goal has been to elucidate whether the interaction of CrO 4 2Ϫ on Al alloy surfaces is in certain aspects analogous to that of MoO 4 2Ϫ on stainless steel surfaces and investigate whether a bipolar mechanism is applicable to aluminum surfaces. The aluminum hydroxide film was freshly formed on the metal surface and exposed to chromate and chloride solutions. Both chromate and chloride ions were observed to lead to a structural change in the hydrated aluminum anodic film consistent with deprotonation. Although both lead to deprotonation, exposure to chromate resulted in a structural transformation to an oxide layer associated with higher corrosion resistance and exposure to chloride lead to the formation of an oxyhydroxide film that is associated with a lower corrosion resistance. When the alloy was exposed to chromate prior to chloride exposure, the adsorbed chromate acted as a fixed negative charge substantially inhibiting chloride ingress. A reaction scheme, involving the formation of aluminum hydroxychlorides, has been proposed for deprotonation due to chloride. Deprotonation by chromate is explained for the first time in terms of bipolarity. Evidence suggests that two models may be operative on the surface of roughened AA106.Sakashita and Sato 1,2 have presented a molecular mechanism for metal passivation, in which a bipolar film consists of an anion selective hydrated oxide film on the metal with a cation selective layer in contact with the solution. This mechanism was shown to be active on thick films formed on iron. 1,2 It is well known that deprotonation within a film may occur at an applied anodic passivating potential thereby leading to the formation of a crystalline oxide inner layer and a hydrated gel-like outer layer. Deprotonation is a field-driven process and hence will be supported by a bipolar film that acts like an ionic rectifier, with its anion selective inner layer and cation selective outer layer. Hydrogen ions from bound water or hydroxide will be expelled from the film and the oxygen ion will migrate toward the metal, thickening the oxide barrier layer. The effectiveness of MeO 4 2Ϫ ions as cation selective agents may be explained using the pioneering work by Rozenfeld and Larkin, wherein the authors attempt to explain the electron distribution on the electron acceptor molecules using quantum mechanical calculations and experimental data to support it. 3-5 According to these calculations, the additional electrons reside on the oxygen ligands, thus increasing their negative fixed charge and it is this fixed negative charge that accounts for the cation-selective outer film. This is contrary to the expectation that the high positive charge residing on the core metal atom will attract electrons, thereby resulting in a fixed...

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The structure and configuration of pseudomonic acid C

Cited by 39 publications

References 8 publications

Biosynthesis of Mupirocin by Pseudomonas fluorescens NCIMB 10586 Involves Parallel Pathways

Biosynthesis of Mupirocin by Pseudomonas fluorescens NCIMB 10586 Involves Parallel Pathways

Mutational Analysis Reveals That All Tailoring Region Genes Are Required for Production of Polyketide Antibiotic Mupirocin by Pseudomonas fluorescens

A Duplex Mechanism-Based Model for the Interaction Between Chromate Ions and the Hydrated Oxide Film on Aluminum Alloys

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