- Ralstonins A and B, Lipopeptides with Chlamydospore-Inducing and Phytotoxic Activities from the Plant Pathogen Ralstonia solanacearum
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Ralstonia solanacearum has an orphan hybrid polyketide synthase-nonribosomal peptide synthetase gene cluster. We herein isolate its products (named ralstonins A and B) from R. solanacearum and elucidate their structures and biological activities. Ralstonins are unusual lipodepsipeptides composed of 11 amino acids (containing unique amino acids such as β-hydroxytyrosine and dehydroalanine) and a 3-amino-2-hydroxyoctadecanoic acid, and their production is controlled by quorum sensing, a mechanism of bacterial cell-cell communication. Ralstonins exhibited chlamydospore-inducing activity and phytotoxicity.
- Murai, Yuta,Mori, Shoko,Konno, Hiroyuki,Hikichi, Yasufumi,Kai, Kenji
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- Mapping the Binding Motifs of Deprotonated Monounsaturated Fatty Acids and Their Corresponding Methyl Esters within Supramolecular Capsules
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A suite of NMR techniques revealed that a cavitand (1) formed 2:1 host-guest complexes with a range of monounsaturated fatty carboxylates and their corresponding methyl esters. All of the carboxylates bound to the capsule in a J-shaped motif with the carboxylate at the equatorial region of the dimeric capsule, and the reverse turn of the chain and the methyl terminal in each polar region of the host. Guest exchange was slow on the NMR time scale, while tumbling was slow or close to the NMR time scale depending on the position and stereochemistry of the double bond. In contrast, the methyl esters were found to bind in three motifs depending on the position and stereochemistry of the double bond. Thus, the esters were observed to bind in a J-shaped, U-shaped (the turn in the guest occupying a polar region and the two termini competing for occupancy of the other pole), or a reverse J-shaped motif (ester moiety and turn each occupying a pole and the methyl terminal located near the equator). Relative binding constant (Krel) determinations revealed that the affinity for the capsule was dependent on the position and stereochemistry of the double bond.
- Wang, Kaiya,Gibb, Bruce C.
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p. 4279 - 4288
(2017/04/27)
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- Biosynthesis-Assisted Structural Elucidation of the Bartolosides, Chlorinated Aromatic Glycolipids from Cyanobacteria
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The isolation of the bartolosides, unprecedented cyanobacterial glycolipids featuring aliphatic chains with chlorine substituents and C-glycosyl moieties, is reported. Their chlorinated dialkylresorcinol (DAR) core presented a major structural-elucidation challenge. To overcome this, we discovered the bartoloside (brt) biosynthetic gene cluster and linked it to the natural products through in vitro characterization of the DAR-forming ketosynthase and aromatase. Bioinformatic analysis also revealed a novel potential halogenase. Knowledge of the bartoloside biosynthesis constrained the DAR core structure by defining key pathway intermediates, ultimately allowing us to determine the full structures of the bartolosides. This work illustrates the power of genomics to enable the use of biosynthetic information for structure elucidation.
- Le?o, Pedro N.,Nakamura, Hitomi,Costa, Margarida,Pereira, Alban R.,Martins, Rosário,Vasconcelos, Vitor,Gerwick, William H.,Balskus, Emily P.
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supporting information
p. 11063 - 11067
(2016/07/06)
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