Datta Indrani, Banik-Maiti Sarbani, Adhikari Lopa, Sau Subrata, Das Niranjan, Mandal Nitai Chandra
Department of Biochemistry, Bose Institute, Acharya J. C. Bose Birth Centenary Building, P-1/12, CIT Scheme VII M, Calcutta 700 054, India.
J Biochem Mol Biol. 2005 Jan 31;38(1):89-96. doi: 10.5483/bmbrep.2005.38.1.089.
Earlier, we reported that the bacteriophage lambda P gene product is lethal to Escherichia coli, and the E. coli rpl mutants are resistant to this lambda P gene-mediated lethality. In this paper, we show that under the lambda P gene-mediated lethal condition, the host DNA synthesis is inhibited at the initiation step. The rpl8 mutation maps around the 83 min position in the E. coli chromosome and is 94 % linked with the dnaA gene. The rpl8 mutant gene has been cloned in a plasmid. This plasmid clone can protect the wild-type E. coli from lambda P gene-mediated killing and complements E. coli dnaAts46 at 42 degrees C. Also, starting with the wild-type dnaA gene in a plasmid, the rpl-like mutations have been isolated by in vitro mutagenesis. DNA sequencing data show that each of the rpl8, rpl12 and rpl14 mutations has changed a single base in the dnaA gene, which translates into the amino acid changes N313T, Y200N, and S246T respectively within the DnaA protein. These results have led us to conclude that the rpl mutations, which make E. coli resistant to lambda P gene-mediated host lethality, are located within the DNA initiator gene dnaA of the host.
早些时候，我们报道噬菌体λ P基因产物对大肠杆菌具有致死性，而大肠杆菌rpl突变体对这种λ P基因介导的致死性具有抗性。在本文中，我们表明在λ P基因介导的致死条件下，宿主DNA合成在起始步骤受到抑制。rpl8突变位于大肠杆菌染色体上约83分钟位置附近，与dnaA基因的连锁率为94%。rpl8突变基因已被克隆到一个质粒中。该质粒克隆可以保护野生型大肠杆菌免受λ P基因介导的杀伤，并在42℃时互补大肠杆菌dnaAts46。此外，从质粒中的野生型dnaA基因开始，通过体外诱变分离出了rpl样突变。DNA测序数据表明，rpl8、rpl12和rpl14突变中的每一个都在dnaA基因中改变了一个单一碱基，分别在DnaA蛋白内转化为氨基酸变化N313T、Y200N和S246T。这些结果使我们得出结论，使大肠杆菌对λ P基因介导的宿主致死性具有抗性的rpl突变位于宿主的DNA起始基因dnaA内。
