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

本文报道了产硫链霉菌S.C.的接合质粒转移和细胞间前孢子染色体分裂过程中的事件和复制。Azureus和S.Iaurentis.我们确定了与质粒DNA和前孢子染色体DNA转移有关的基因或蛋白质，如转移基因(分别由质粒和宿主染色体编码的trA和spIIIE样基因)、复制因子(ORI、rep)和单链DNA结合蛋白、组蛋白样蛋白基因(Hup)及其产物。这些数据和观察结果表明。质粒和前孢子染色体DNA的移位可能是通过在ORI处引入缺口来形成单链DNA而触发的，单链DNA转移的能量来自于具有ATP结合位点的TrA和SpoIIIE样跨膜蛋白上的ATP水解。Hup基因产物包被单链DNA也可能发生在转位过程中和在受体细胞中。虽然SpoIIIE类蛋白对链霉菌细胞的产孢量是必需的，但由于两个基因在结构和功能上的相似性，TrA蛋白似乎通过竞争抑制了它们的产孢量。这也表明，类spIIIE基因在分离后的染色体分裂中也是重要的。多肽抗生素杆菌素可抑制该质粒的转移。相反，它刺激了前孢子的分配。分离到杆菌素诱导的两种膜蛋白(32 kDa和38 kDa)，前者未知，后者为ABC转运蛋白。这些蛋白质可能参与了质粒转移和前孢子染色体分裂之间的竞争。另一方面，我们还确定了接合线状质粒的特性，它抑制了接合环状质粒的伤害性(抑制产孢量和硫链霉菌素产量)。

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.