39 新規翻訳後修飾の解明 : ComXフェロモンの構造決定と化学合成(口頭発表の部)

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The ComX pheromone is a posttranslationally modified oligopeptide that stimulates natural competence, controlled by quorum sensing in Bacillus subtilis. The ComX pheromone possesses a tryptophan residue, which is modified by isoprenylation, but the precise structure is not known. To elucidate the precise nature of the ComX modification, we determined the molecular formula of ComX_<RO-E-2> pheromone from the strain RO-E-2, and assumed the modification might be a simple substitution of a tryptophanyl proton by a geranyl group. Then we synthesized the ComX_<RO-E-2> peptides containing 6 kinds of geranylated tryptophans. Although each synthetic peptide had similar hydrophobicity to the natural pheromone, but none had biological activity. Using a previously reported Escherichia coli expression system, we optimized the culture and purification conditions. We isolated the ComX_<RO-E-2> pheromone, observed NMR spectra, and determined the structure for the tryptophan residue in ComX_<RO-E-2> pheromone. Furthermore, we carried out a conformational search, and proposed its absolute stereochemistry. To confirm the stereochemistry, we synthesized the corresponding ComX_<RO-E-2> peptide and other diastereomers. The proposal ComX_<RO-E-2> peptide only showed an identical ^1H NMR spectrum to that of the natural pheromone, and a very similar biological activity. We have thus succeeded in synthesizing the ComX_<RO-E-2> pheromone and determining the absolute structure of the pheromone. The novel posttranslational modification of the ComX_<RO-E-2> pheromone, showing that addition of a geranyl group to a tryptophan residue results in the formation of a unique ring structure.
天然有機化合物討論会の論文
2005-09-15

39 新規翻訳後修飾の解明 : ComXフェロモンの構造決定と化学合成(口頭発表の部)

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