P-6 Cyclothiazomycin B1,B2の単離・構造とリボソーム依存型GTPase阻害活性(ポスター発表の部)

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Novel cyclic thiopeptides, cyclothiazomycins B1 (1) and B2 (2) were isolated from Streptomyces sp. A307 as potent hyphal swelling inducing substances. The ESIMS of 1 provided the molecular weight to be 1527. The number of exchangeable protons was established by the increased mass number measured in the presence of D_2O. Since the HRS data was not sufficient to establish the molecular formula, it was estimated by combined analysis with subsequent NMR studies and with structures of the hydrolysates. The ^1H and ^<13>C NMR spectroscopic analysis of 1 detected 53 nonexchangeable protons and 60 carbons. Consideration of the original amino acids suggested one more carbon as well as number of other heteroatoms, nitrogen, oxygen, and sulfur to establish the molecular formula to be C_<61>H_<69>N_<21>O_<13>S_7 which is in good accordance with that obtained by HRESIMS. The sequence of the amino acid residues were examined by FGHMBC and ROESY, and was further confirmed by MALDI-TOF/TOF. The Marfey's method revealed L-configurations for the arginine, proline and cysteine residues. Aspartic acid residue was detected as racemate to establish the total structure of 1, an arginine analogues of cyclothiazomycin, as shown bellow. The detailed ^1H NMR spectral comparison between those of 1 and 2 led to elucidate the structure of 2 which is a stereoisomer of the dehydrohomoalanine moiety (DHHAI) adjacent to the proline residue. The subsequent biological investigation disclosed that pure samples of these cyclic thiopeptides induced potent hyphal swelling against Cochliobolus miyabeanus which is more effective than commercial agrochemical polyoxin. Interestingly, 1 inhibited transcription from DNA for dihydrofolate reductase by RNA polymerase from bacteriophage T7 and SP6. Since there are few inhibitors for bacteriophage RNA polymerase 1 would be a powerful tool for transcription studies.
天然有機化合物討論会の論文
2006-09-15

P-6 Cyclothiazomycin B1,B2の単離・構造とリボソーム依存型GTPase阻害活性(ポスター発表の部)

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