Seto H, Tomasz A
Proc Natl Acad Sci U S A. 1974 Apr;71(4):1493-8. doi: 10.1073/pnas.71.4.1493.
Ethylenediaminetetraacetate and other divalent-cation-complexing agents greatly stimulate the cellular binding of DNA molecules to competent pneumococci, while the appearance of genetic transformants and nuclease-resistant DNA binding are completely inhibited. Based on this finding, we developed an experimental system in which three early and consecutive stages of genetic transformation can be experimentally separated: (i) attachment of DNA molecules to cell surface sites that are only demonstrable in the competent state; (ii) a divalent-cation-dependent nucleolytic splitting and release of the adsorbed molecules to the medium; and (iii) emergence of potential transformants accompanied by an energy-requiring and divalent-cation-dependent process in which the cell-associated DNA molecules become inaccessible to shearing forces, nucleases, anti-DNA serum, and polycations.
乙二胺四乙酸及其他二价阳离子络合剂能极大地刺激DNA分子与感受态肺炎球菌的细胞结合，而遗传转化体的出现及核酸酶抗性DNA结合则完全受到抑制。基于这一发现，我们开发了一个实验系统，在该系统中，遗传转化的三个早期且连续的阶段能够通过实验分离：（i）DNA分子附着于仅在感受态状态下才可证明的细胞表面位点；（ii）吸附分子经二价阳离子依赖的核酸水解裂解并释放至培养基中；（iii）潜在转化体的出现伴随着一个需要能量且依赖二价阳离子的过程，在此过程中，细胞相关的DNA分子对剪切力、核酸酶、抗DNA血清及聚阳离子变得不可接近。
