Tranlocation of Conjugative Plasmid and Prespore Chromosome across Membrane during Sporulation in Streptomyces

本文报道了产硫链蛋白链霉菌、S.c. azureus和s.c iaurentitis细胞间共轭质粒转移和孢子前染色体分配过程中的事件和复制。我们确定了与质粒DNA和孢子前染色体DNA转移功能相关的基因或蛋白质，如转移基因（分别由质粒和宿主染色体编码的tra和spoiie样基因）、复制因子（ori、rep）和ssdna结合蛋白。组蛋白样蛋白基因及其产物。这些数据和观察表明：质粒和孢子前染色体DNA的易位可以通过引入一个缺口来形成ssDNA而触发。ssDNA转移的能量来源于ATP在Tra和spoiie样跨膜蛋白上的水解，它们具有ATP结合位点。在易位和受体细胞中，也可能发生hup基因产物包裹ssDNA的情况。尽管spoiie样蛋白对于链霉菌细胞的产孢是必需的，但由于两种基因的结构和功能相似性，Tra蛋白似乎通过竞争抑制它们的产孢。研究还表明，spoiiie样基因在分离后染色体分裂中也起重要作用。质粒的转移被一种多肽抗生素结核菌素抑制。相反，它促进了孢子前分裂。分离到两种杆菌肽诱导的膜蛋白（32和38 kDa），前者是未知的，后者是abc转运蛋白。这些蛋白可能参与质粒转移和孢子前染色体分裂之间的竞争。另一方面，我们还确定了一种共轭线性质粒的特性，该特性抑制了共轭环状质粒的有害作用（抑制产孢和硫链蛋白产量）。

This report concerns events and replication during the conjugative plasmid trasnfer and prespore chromosome partitioning between the cells in thiostrepton-producing Strep tomyces, S.c. azureus and S.Iaurentii.We determined the genes or proteins functionaly related to the transfer of plasmid DNA and prespore chromosome DNA, such as trasfer genes (tra and spoIIIE-like gene encoded by plasmid and host chromosome, respectively), replication factors (ori, rep) , and ssDNA-binding protein, histone-like protein gene (hup), and their products. These data and observation suggested as follows. Translocation of plasmid and prespore chromosome DNA may be triggered by introduction of a nick at ori to form ssDNA.The energy of ssDNA transfer would derive from by the hydrolysis of ATP on the Tra and SpoIIIE-like transmenbrane proteins, which have an ATP binding site. Coating of ssDNA by hup gene product may also occur during the translocation and in the recipient cell. Although the SpoIIIE-like protein would ben ecessary for sporulation in Streptomyces cells, Tra protein seems to inhibit their sporulation by a competition, owing to structural and functional similarities of both genes. It is also suggested that spoIIIE-like gene is also important in postseptational chromosome partitioning. The plasmid transfer was inhibited by a peptide antibiotic bacitracim. On the contrary, the prespore partitioning was stimulated by it. Two bacitracin-induced menbrane proteins (32 and 38 kDa) were isolated : the former was unknown, but the latter was ABC-transporter. These proteins may participate in the competition between plasmid transfer and prespore chromosome partitioning.On the other hand, we also determined the characteristics of a conjugative linear plasmid, which suppressed the injurious effects (inhibition of sporulation and thiostrepton productivity) of conjugative circular plasmid.