| Co-Investigator(Kenkyū-buntansha) |
KIMURA Makoto Department of Agriculture, KYUSHU UNIVERSITY,Ass.Prof., 農学部, 助教授 (10204992)
DOI Katsumi Department of Agriculture, KYUSHU UNIVERSITY,Ass.Prof., 農学部, 講師 (40253520)
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| Research Abstract |
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.
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