Buchstein S R, Hinkle D C
Mol Gen Genet. 1982;188(2):211-8. doi: 10.1007/BF00332677.
The Escherichia coli mutants 7009 and BR3 are defective in the growth of bacteriophage T7. We have previously shown that both of these mutant hosts produce an altered RNA polymerase which is resistant to inhibition by the T7 gene 2 protein (De Wyngaert and Hinkle 1979). In both strains, the mutation which prevents T7 growth is closely linked to rifA (rpoB). Both mutants are complemented by transformation with a multicopy plasmid carrying rpoB and rpoC but not by a plasmid carrying only rpoB. This indicates that the mutations reside in rpoC, the structural gene for the beta' subunit of RNA polymerase. When a single copy of the wildtype rpoC allele is introduced into the mutant using the transducing phage lambda drifd18, the mutant allele is dominant over wildtype. The lambda drifd18 transductant also remains unable to support the growth of T7 in the presence of rifampin. This supports our conclusion that the mutation is in rpoC. We have measured the growth of T7 phage, the kinetics of phage DNA synthesis, and the structure of replicative DNA intermediates in several transductants, and compared these results with those obtained in the original mutant strains.
大肠杆菌突变体7009和BR3在噬菌体T7的生长方面存在缺陷。我们之前已经表明，这两种突变宿主都产生了一种改变的RNA聚合酶，该酶对T7基因2蛋白的抑制具有抗性（德温加特和欣克尔，1979年）。在这两种菌株中，阻止T7生长的突变都与rifA（rpoB）紧密连锁。这两种突变体都可以通过携带rpoB和rpoC的多拷贝质粒转化得到互补，但不能通过仅携带rpoB的质粒得到互补。这表明突变位于rpoC，即RNA聚合酶β'亚基的结构基因中。当使用转导噬菌体λdrifd18将野生型rpoC等位基因的单拷贝引入突变体时，突变等位基因对野生型是显性的。在存在利福平的情况下，λdrifd18转导子也仍然无法支持T7的生长。这支持了我们关于突变位于rpoC的结论。我们已经测量了几种转导子中T7噬菌体的生长、噬菌体DNA合成的动力学以及复制性DNA中间体的结构，并将这些结果与在原始突变菌株中获得的结果进行了比较。
