TRANSCRIPTIONAL ORGANIZATION AND REGULATION OF AN ANTIBIOTIC EXPORT COMPLEX IN THE PRODUCING STREPTOMYCES CULTURE
TRANSCRIPTIONAL ORGANIZATION AND REGULATION OF AN ANTIBIOTIC EXPORT COMPLEX IN THE PRODUCING STREPTOMYCES CULTURE
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DOI：
10.1007/bf00260629
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发表时间：
1991-09-01
期刊：
影响因子：
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通讯作者：
HOPWOOD, DA
中科院分区：
文献类型：
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作者：
CABALLERO, JL;MALPARTIDA, F;HOPWOOD, DA
天蓝色链霉菌A3（2）放线菌红素生物合成基因簇的actII区域中的三个开放阅读框（ORF），其参与抗生素的输出，在两个不同的转录物上进行。单顺反子转录物携带actII-ORF 1，编码推定的阻遏蛋白，双顺反子转录物编码actII-ORF 2和-ORF 3，其产物被假定形成抗生素输出复合物。actII-ORF 1和actII-ORF 2/3转录物各自具有单个启动子，并且两种转录物的启动子重叠。这两种启动子在已发展到放线菌紫素生产阶段的培养物中最活跃。启动子类似于大肠杆菌和链霉菌中营养级的共有启动子。我们还证明这些启动子在大肠杆菌中表达。大肠杆菌，并利用这一发现揭示了一个调节作用的阻遏物，使用xylE报告基因的启动子探针穿梭载体和调节表达的actII-ORF 1基因的控制下的P（lac）。actII-ORF 2/3启动子被ORF 1产物强烈抑制，ORF 1产物也抑制其自身的启动子。这一发现的运营商/启动子的安排，监管互联，抗生素出口/阻遏基因对链霉菌惊人的相似，四环素耐药的细菌的临床重要性支持的假设，这些基因的进化起源的祖先放线菌。
Three open reading frames (ORFs) in the actII region of the actinorhodin biosynthetic gene cluster of Streptomyces coelicolor A3(2), which are involved in the export of the antibiotic are carried on two divergent transcripts. A monocistronic transcript carries actII-ORF1, encoding a putative repressor protein, and a bicistronic transcript codes for actII-ORF2 and -ORF3, whose products have been postulated to form an antibiotic export complex. The actll-ORF1 and actII-ORF2/3 transcripts each have a single promoter and the promoters for the two transcripts overlap. Both promoters are most active in cultures that have developed to the stage of actinorhodin production. The promoters resemble consensus promoters of the vegetative class in Escherichia coli and Streptomyces. We also demonstrate that these promoters are expressed in E. coli and use this finding to reveal a regulatory role for the repressor, using the xylE reporter gene on promoter-probe shuttle vectors and regulated expression of the actII-ORF1 gene under control of P(lac). The actII-ORF2/3 promoter is strongly repressed by the ORF1 product and the ORF1 product also represses its own promoter. The finding that the operator/promoter arrangement, and regulatory interconnection, of an antibiotic export/repressor gene pair in Streptomyces strikingly resemble those for tetracycline resistance in bacteria of clinical importance supports the hypothesis of an evolutionary origin of such genes in an ancestral actinomycete.