Serratia plymuthica strain RVH1, initially isolated from an industrial food processing environment, displays potent antimicrobial activity towards a broad spectrum of Gram-positive and Gram-negative bacterial pathogens. Isolation and subsequent structure determination of bioactive molecules led to the identification of two polyamino antibiotics with the same molecular structure as zeamine and zeamine II as well as a third, closely related analogue, designated zeamine I. The gene cluster encoding the biosynthesis of the zeamine antibiotics was cloned and sequenced and shown to encode FAS, PKS as well as NRPS related enzymes in addition to putative tailoring and export enzymes. Interestingly, several genes show strong homology to the pfa cluster of genes involved in the biosynthesis of long chain polyunsaturated fatty acids in marine bacteria. We postulate that a mixed FAS/PKS and a hybrid NRPS/PKS assembly line each synthesize parts of the backbone that are linked together post-assembly in the case of zeamine and zeamine I. This interaction reflects a unique interplay between secondary lipid and secondary metabolite biosynthesis. Most likely, the zeamine antibiotics are produced as prodrugs that undergo activation in which a nonribosomal peptide sequence is cleaved off. 相似文献
In the context of our ongoing study of vitamin D structure-function relationships and in an attempt to obtain a better dissociation of their prodifferentiating (HL-60) and/or antiproliferative (MCF-7) activities and their calcemic activity, further 20-epi and 14-epi modifications were made to three trans-decalin CD-ring analogs of 1,25-dihydroxyvitamin D(3), the hormonally active metabolite of vitamin D(3), possessing a natural 20R side chain and featuring additional structural modifications in the seco-B-ring and in the A-ring. Following a previously observed trend and in agreement with the conformational analysis results, all three 20-epi derivatives show substantially lower biological activities, opposite to what is usually observed for analogs having the natural CD-ring. The 14-epi modification (cis-decalins) has little effect on the biological activity of the ynediene type and the saturated derivative, but results in an approximate 10-fold reduction in activity of the previtamin derivative. No better dissociation of the prodifferentiating and/or antiproliferative activities and the calcemic activity was achieved. 相似文献
The extraction procedure and quantitative determination by HPLC-evaporative light scattering detection (ELSD) of the main bioactive components, namely, imperialine (1) and imperialine-3 beta-glucoside (2), of bulbs of Fritillaria pallidiflora Schrenk have been investigated. The most efficient method for the simultaneous extraction of 1 and 2 involved pre-treatment of the bulb powder with ammonia, followed by reflux with dichloromethane:methanol at 90 degrees C for 4 h. Simultaneous determination of non-chromophoric 1 and 2 by HPLC-ELSD employed a Kromasil C18 column eluted with acetonitrile:water:diethylamine. The assay was accurate and reproducible with an overall variation lower than 4% and a sample recovery higher than 98%. The methods described have been successfully used to evaluate the quality of three batches of the crude traditional Chinese medicinal herb derived from the bulbs of F. pallidiflora. 相似文献
Cellular and Molecular Neurobiology - Tumor necrosis factor receptor-associated factor 6 (TRAF6) has been reported to be expressed in spinal astrocytes and is involved in neuropathic pain. In this... 相似文献
(99m)Technetium-labeled diethylenetriamine pentaacetic acid-polyethylene glycol-folate (DTPA-PEG-folate) was synthesized and tested as a radiopharmaceutical agent, which targeted the lymphatic system with metastatic tumor. Folic acid was reacted with H2N-PEG-NH2 to yield H2N-PEG-folate. After purification by anion-exchange chromatography, the product was reacted with cyclic DTPA. By removal of unreacted DTPA by size-exclusion chromatography, DTPA-PEG-Folate was obtained. Fluorescein-5-isothiocyanate (FITC)-labeled DTPA-PEG-folate and DTPA-PEG-OCH3 were prepared via a dicyclohexylcarbodiimide-mediated coupling. In vitro competitive binding test showed that the uptake of [125I] folic acid was inhibited by DTPA-PEG-folate and the 50% inhibitory concentration was 4.37 pmol/L (R2 = 0.9922). The relative affinity of DTPA-PEG-FITC was 0.18 for human folate receptor comparing with folic acid. In cultured tumor cells, uptake of fluorescence-labeled DTPA-PEG-folate was found to increase significantly in folate-deficient medium compared with that of untargeted DTPA-PEG-OCH3 and FITC-ethylenediamine. The competition with free folic acid blocked the cell uptake of DTPA-PEG-folate. These results confirmed the DTPA-PEG-folate entered into KB cells through the folate receptor endocytosis pathway in vitro. The radiolabeled yield of [(99m)Tc] DTPA-PEG-folate was in excess of 98%, and specific activities of 7.4 kBq (0.2 microCi/microg) were achieved. After subcutaneous injection, [(99m)Tc] DTPA-PEG-folate exhibited an initial increase and successive decline of accumulation in popliteal nodes in normal Wistar rats. Expect for the kidney, uptake by other tissues was rather low. In a normal rabbit imagine study, the lymphatic vessels were readily visualized by single-photon-emission computed tomography following subcutaneous injection of [(99m)Tc] DTPA-PEG-folate. In conclusion, the [(99m)Tc] DTPA-PEG-folate conjugate may have a potential as a lymphatic tumor-targeted radiopharmaceutical. 相似文献
Plant iron (Fe) deficiency is widely present in alkaline calcium soils worldwide, and endophytes show great potential for promoting plant nutrient absorption. However, the underlying mechanisms remain unclear. To clarify the mechanisms by which the endophytic fungus Phomopsis liquidambaris promotes peanut Fe absorption, we designed this study to detect the physiological changes in peanut with P. liquidambaris infection. We measured ethylene and auxin in peanuts under Fe deficiency and found that fungal colonization promoted their accumulation (50% and 20%, respectively, at the top point). Moreover, plant Fe absorption ability and transfer were enhanced according to qPCR and enzyme results; the Fe content in the leaf increased (29.52%) as the symptoms of leaf chlorosis were ameliorated. Finally, the chlorophyll content increased (29%), and plant growth was enhanced (13.3%). We also proved that during Fe insufficiency, auxin functions downstream of ethylene to induce the upregulation of Fe absorption-related gene and enzyme activity including that of AHA4, IRT1, H+-ATPase, and FCR. We conclude that the addition of P. liquidambaris activates the auxin signaling pathway downstream of ethylene and improves peanut Fe absorption by promoting rhizosphere acidification, increasing FCR and IRT1 expression in peanut roots, leading to plant Fe absorption and growth.