Schuster H, Schlicht M, Lanka E, Mikolajczyk M, Edelbluth C
Mol Gen Genet. 1977 Feb 28;151(1):11-6. doi: 10.1007/BF00446907.
An Escherichia coli K12 dnaB dnaC mutant was constructed by P1 transduction of the dnaC allele into a dnaB recipient stain. dnaB dnaC transductant were discriminated from dnaB mutants by their inability to grow at 40 degree C after lysogenization with phage P1bac. The dnaB dnaC mutant character was verified by 1. P1 transduction, and 2. by in vitro complementation with dnaB and dnaC wild type protein fractions. DNA synthesis was studied in strains containing dnaB, dnaB dnaC alleles in an otherwise uniform genetic background with the dnaB character either unsuppressed or suppressed by P1bac prophage. Degradation at 42 degree C of [3H]-thymidine pulse-labeled DNA in dnaB and dnaB dnaC mutants is suppressed by P1bac. However, unlike the dnaC mutant, the P1bac lysogen of the dnaB dnaC mutant exhibits an abrupt cessation of DNA synthesis and less residual cell divisions at 42 degree C indicating an inhibition of DNA chain elongation rather than a defect in DNA initiation. It is suggested that denaturation of the dnaB protein effects the dnaC function.
通过将dnaC等位基因经P1转导导入dnaB受体菌株，构建了大肠杆菌K12 dnaB dnaC突变体。通过用噬菌体P1bac溶源化后在40℃下无法生长，将dnaB dnaC转导子与dnaB突变体区分开来。通过以下两点验证了dnaB dnaC突变体的特性：1. P1转导；2. 用dnaB和dnaC野生型蛋白组分进行体外互补。在遗传背景基本一致的菌株中，研究了含有dnaB、dnaB dnaC等位基因且dnaB特性未被P1bac原噬菌体抑制或被其抑制的菌株中的DNA合成。P1bac可抑制dnaB和dnaB dnaC突变体中[3H] - 胸腺嘧啶脉冲标记DNA在42℃下的降解。然而，与dnaC突变体不同，dnaB dnaC突变体的P1bac溶源菌在42℃时表现出DNA合成突然停止且残留细胞分裂减少，这表明是DNA链延伸受到抑制，而非DNA起始存在缺陷。有人提出，dnaB蛋白的变性影响了dnaC的功能。
