MEMBRANE LOCATION OF A DEOXYRIBONUCLEASE IMPLICATED IN GENETIC TRANSFORMATION OF DIPLOCOCCUS-PNEUMONIAE
MEMBRANE LOCATION OF A DEOXYRIBONUCLEASE IMPLICATED IN GENETIC TRANSFORMATION OF DIPLOCOCCUS-PNEUMONIAE
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DOI：
10.1128/jb.124.3.1321-1329.1975
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发表时间：
1975-01-01
影响因子：
3.2
通讯作者：
NEUBERGER, M
中科院分区：
文献类型：
--
作者：
LACKS, S;NEUBERGER, M
用原生质球分级法研究了肺炎双球菌中酶的细胞定位。在遗传转化过程中，一种与脱氧核糖核酸（DNA）进入细胞有关的脱氧核糖核酸酶位于细胞膜上。这种酶是细胞的主要内切核酸酶（内切核酸酶I），它是将供体DNA转化为细胞内的单链和细胞外的寡核苷酸所必需的，因此可以在细胞表面起作用。另一种酶，细胞壁溶素（自溶素），也被发现在膜部分。其他酶，包括淀粉麦芽糖酶，两个核酸外切酶，和腺苷三磷酸依赖性脱氧核糖核酸酶，和限制性内切酶，位于细胞内的胞质溶胶。没有一种酶主要是周质的位置。肺炎球菌细胞在浓糖溶液中孵育时自发获得球体。自溶酶似乎参与了这一过程。生理上有能力摄取DNA的细胞形成对DNA敏感的原生质球的速度比没有能力的细胞快两到三倍。虽然一些遗传缺陷突变体形成原生质球的速度较慢，但其他突变体形成原生质球的速度更快。
The cellular localization of enzymes in Diplococcus pneumoniae was examined by fractionation of spheroplasts. A deoxyribonuclease implicated in the entry of deoxyribonucleic acid (DNA) into the cell during genetic transformation was located in the cell membrane. This enzyme, the major endonuclease of the cell (endonuclease I), which is necessary for the conversion of donor DNA to single strands inside the cell and oligonucleotides outside, thus could act at the cell surface. Another enzyme, the cell wall lysin (autolysin), was also found in the membrane fraction. Other enzymes, including amylomaltase, two exonucleases, and adenosine triphosphate-dependent deoxyribonuclease, and a restriction type endonuclease, were located in the cytosol within the cell. None of the enzymes examined were predominantly periplasmic in location. Spheroplasts were obtained spontaneously on incubation of pneumococcal cells in concentrated sugar solutions. The autolytic enzyme appears to be involved in this process. Cells that were physiologically competent to take up DNA formed osmotically sensitive spheroplasts two to three times faster than cells that were not in the competent state. Although some genetically incompetent mutants also formed spheroplasts more slowly, other such mutants formed them at the faster rate.