Lloyd R G, Thomas A
Mol Gen Genet. 1984;197(2):328-36. doi: 10.1007/BF00330981.
Conjugational recombination in Escherichia coli was investigated by measuring lacZ+ product, beta-galactosidase, in crosses between lacZ mutants. Enzyme production in both Hfr and F-prime crosses was detected very soon after transfer of the donor lacZ allele. The level of enzyme activity was reduced by no more than two-fold when the recipient carried a recB mutation. With an F-prime donor, recombination appeared to be restricted largely to a short period immediately after transfer, with little evidence of recombination during subsequent exponential growth of the transconjugant cells. These observations are interpreted to suggest that recA dependent recombination is able to initiate with high efficiency at gaps present in the donor DNA before synthesis of a complementary strand is completed, and independently of recB function. A molecular model for conjugational recombination based on this idea is presented in terms of the known activities of recA and recBC products. Some of the predictions of the model are tested by analysing the recombinant genotypes produced in Hfr crosses with multiply marked strains.
通过测量lacZ突变体之间杂交中的lacZ +产物β-半乳糖苷酶，对大肠杆菌中的接合重组进行了研究。在供体lacZ等位基因转移后不久，就在Hfr和F'杂交中检测到了酶的产生。当受体携带recB突变时，酶活性水平降低不超过两倍。对于F'供体，重组似乎主要局限于转移后紧接着的短时间内，在转接合子细胞随后的指数生长过程中几乎没有重组的证据。这些观察结果被解释为表明recA依赖性重组能够在互补链合成完成之前，在供体DNA中存在的缺口处高效启动，并且独立于recB功能。基于这一观点，根据recA和recBC产物的已知活性，提出了一个接合重组的分子模型。通过分析与多重标记菌株的Hfr杂交中产生的重组基因型，对该模型的一些预测进行了检验。
