近日,，中科院南海海洋研究所鞠建華研究員團(tuán)隊(duì)通過(guò)基因組測(cè)序和生物信息學(xué)分析,，發(fā)現(xiàn)灰綠霉素和綠灰霉素的生物合成基因簇結(jié)構(gòu)以轉(zhuǎn)運(yùn)蛋白基因sgvT2為中心，上游區(qū)段負(fù)責(zé)綠灰霉素合成,、下游區(qū)段負(fù)責(zé)合成綠灰霉素的域,，在兩個(gè)區(qū)段外則是調(diào)控基因和抗性基因區(qū)。
研究人員運(yùn)用RT-PCR技術(shù)對(duì)野生型和突變株進(jìn)行分析,，發(fā)現(xiàn)它與受體的結(jié)合能夠激活下游的兩個(gè)SARP家族的正調(diào)控蛋白sgvT2和sgvT3,，從而揭示了灰綠霉素和綠灰霉素高效協(xié)同抗菌性的生物合成機(jī)制。該成果被選為內(nèi)封面文章發(fā)表在ChemBioChem上,。
據(jù)介紹,，灰綠霉素（Griseovridin）和綠灰霉素（Viridogrisein）是一對(duì)由多種放線菌生產(chǎn)的具有協(xié)同抗菌效應(yīng)的鏈陽(yáng)菌素類抗生素?；揖G霉素具有二十三元不飽和并九元含烯硫鍵的內(nèi)酯結(jié)構(gòu),，綠灰霉素具有三個(gè)天然氨基酸和五個(gè)非天然氨基酸構(gòu)成的八元環(huán)脂肽結(jié)構(gòu)?；揖G霉素可作用于細(xì)菌50S核糖體的A位點(diǎn),，阻止氨酰tRNA的結(jié)合，有利于綠灰霉素高效結(jié)合P位點(diǎn),，加速延生的多肽鏈解離,，二者協(xié)同作用能顯著提高抑菌效果。兩種抗生素結(jié)構(gòu)獨(dú)特,，調(diào)控機(jī)制新穎,，在治療耐藥性病菌感染中具有良好的應(yīng)用前景。
該研究獲得了973計(jì)劃項(xiàng)目,、國(guó)家自然科學(xué)基金和中科院“百人計(jì)劃”人才基金的資助,。(生物谷Bioon.com)
DOI: 10.1002/cbic.201200584
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PMID:
Identification of the Biosynthetic Gene Cluster and Regulatory Cascade for the Synergistic Antibacterial Antibiotics Griseoviridin and Viridogrisein in Streptomyces griseoviridis
Yunchang Xie1,2, Dr. Bo Wang1, Jing Liu1,2,Junchao Zhou1,2, Dr. Junying Ma1, Dr. Hongbo Huang1, Prof. Dr. Jianhua Ju1,*
Griseoviridin (GV) and viridogrisein (VG, also referred to as etamycin), produced by Streptomyces griseoviridis, are two chemically unrelated compounds belonging to the streptogramin family. Both of these natural products demonstrate broad-spectrum antibacterial activity and constitute excellent candidates for future drug development. To elucidate the biosynthetic machinery associated with production of these two unique antibiotics, the gene cluster responsible for both GV and VG production was identified within the Streptomyces griseoviridis genome and characterized, and its function in GV and VG biosynthesis was confirmed by inactivation of 30 genes and complementation experiments. This sgv gene cluster is localized to a 105 kb DNA region that consists of 36 open reading frames (ORFs), including four nonribosomal peptide synthetases (NRPSs) for VG biosynthesis and a set of hybrid polyketide synthases (PKS)-NRPSs with a discrete acyltransferase (AT), SgvQ, to assemble the GV backbone. The enzyme encoding genes for VG versus GV biosynthesis are separated into distinct “halves” of the cluster. A series of four genes: sgvA, sgvB, sgvC, and sgvK, were found downstream of the PKS-NRPS; these likely code for construction of a γ-butyrolactone (GBL)-like molecule. GBLs and the corresponding GBL receptor systems are the highest ranked regulators that are able to coordinate the two streptomyces antibiotic regulatory protein (SARP) family positive regulators SgvR2 and SgvR3; both are key biosynthetic activators. Models of GV, VG, and GBL biosynthesis were proposed by using functional gene assignments, determined on the basis of bioinformatics analysis and further supported by in vivo gene inactivation experiments. Overall, this work provides new insights into the biosyntheses of the GV and VG streptogramins that are potentially applicable to a host of combinatorial biosynthetic scenarios.
