1987 Fiscal Year Final Research Report Summary
Transmissible plasmid genes increase membrane permeability: function and regulatory mechamism of gene expression.
| Project/Area Number |
61570212
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
細菌学
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| Research Institution | The University of Tokushima |
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Principal Investigator |
AKIMOTO Shigeru School of Medicine, The University of Tokushima, 医学部, 講師 (10159337)
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| Co-Investigator(Kenkyū-buntansha) |
ONO Tsuneko School of Medicine, The University of Tokushima, 医学部, 助手 (40035514)
OHNISHI Yoshinari School of Medicine, The University of Tokushima, 医学部, 教授 (10037400)
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| Project Period (FY) |
1986 – 1987
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| Keywords | transmissible plasmid / membrane permeability / RNA degradation / gene expression / RNA polymerase / rifampicin / 転写 |
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| Research Abstract |
srnB is the F-plasmid encoded silent gene whose expression is induced by addition of rifampicin to cause stable RNA degradation. A stem-and-loop structure like a rho-independent terminator was detected in the untranslated leader region. In vitro transcription experiments revealed that most of the transcripts synthesized in the presence of rifampicin were long enough(330 nucleotides) to encode the srnB protein. In the absence of rifampicin, however, most of the transcripts were shorter(65 nucleotide). Nuclease S1 mapping revealed that the short mRNA species initiated at the same site as the long mRNA but terminated within the leader at the 3' end of the terminator-like sequence. A deletion in the stem-loop resulted in constitutive synthesis of the mRNA corresponding to the long mRNA. These results indicate that the rifampicn-bound RNA polymerase can readthrogh the terminator to induce the srnB expression. It has been suggested that the alteration in membrane permeability is a direct effect of the expression of srnB or equivalent gene pnd and that the RNA degradation is a secondary phenomenon. Effects of the gene product on the membrane alteration to increase its permeability is further suggested by the following observations: increase of o-nitrophenyl -D-galactoside uptake, no plasmolysis induction, lysis of spheroplast, and magnesium efflux. We propose here a possible mechamism of stable RNA degradation. The srnB or pnd protein acts on the cytoplasmic membrane to form a kind of pore which allows magnesium to leak to the medium from the cytoplasm. RNase I localized in periplasm can pass through these pores to the cytoplasm. r RNA and tRNA in the lowered concentration of magnesium will then be degraded by RNase I.
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Research Products
(6 results)
