Günther E, Bagdasarian M, Schuster H
Mol Gen Genet. 1984;193(2):225-30. doi: 10.1007/BF00330672.
Fragments of the E. coli chromosome that carry the dnaB groPB534 or groPB612 alleles have been cloned into a cosmid vector. The resulting recombinant plasmids contained the genes uvrA, groP (B534 or B612), and lexA. Further subcloning into high copy number plasmids, during which the uvrA and lexA genes were removed successively, yielded a groPB534 and groPB612 DNA fragment of about 2.4 kb each. Both fragments contained an overlapping 1.8 kb segment of DNA in which the sites of all restriction enzymes tested were identical. The size of these dnaB gene fragments were further delimited by deletion analysis. In E. coli groPB534 in which lambda wild-type and lambda pi A mutants do not replicate (Georgopoulos and Herskowitz 1971) phage replication is rescued if the strain contains the groPB534 gene on high copy number plasmids. On the contrary, in E. coli groPB612, which is temperature-sensitive for its groP character, replication of lambda and lambda pi A is abolished at 30 degrees C if the strain contains the groPB612 recombinant plasmid. On the other hand, replication of lambda pi B remains unaffected whether or not the groP strains harbor the isogenic dnaB gene-containing plasmid. The results suggest that within the cell not only the quality but also the relative amounts of dnaB and lambda P protein are crucial for lambda phage replication.
携带dnaB groPB534或groPB612等位基因的大肠杆菌染色体片段已被克隆到黏粒载体中。所得重组质粒包含uvrA、groP（B534或B612）和lexA基因。进一步亚克隆到高拷贝数质粒中，在此过程中uvrA和lexA基因被相继去除，得到了大小约为2.4 kb的groPB534和groPB612 DNA片段。两个片段都包含一段1.8 kb的重叠DNA片段，其中所有测试的限制酶位点都是相同的。这些dnaB基因片段的大小通过缺失分析进一步确定。在大肠杆菌groPB534中，λ野生型和λ pi A突变体不复制（Georgopoulos和Herskowitz，1971），如果该菌株在高拷贝数质粒上含有groPB534基因，则噬菌体复制得以挽救。相反，在大肠杆菌groPB612中，其groP特性对温度敏感，如果该菌株含有groPB612重组质粒，则在30℃时λ和λ pi A的复制被废除。另一方面，无论groP菌株是否携带含等基因dnaB的质粒，λ pi B的复制均不受影响。结果表明，在细胞内，不仅dnaB和λ P蛋白的质量，而且它们的相对量对λ噬菌体的复制都至关重要。
