DPNA, A METHYLASE FOR SINGLE-STRAND DNA IN THE DPN-II RESTRICTION SYSTEM, AND ITS BIOLOGICAL FUNCTION
DPNA, A METHYLASE FOR SINGLE-STRAND DNA IN THE DPN-II RESTRICTION SYSTEM, AND ITS BIOLOGICAL FUNCTION
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DOI：
10.1073/pnas.86.23.9223
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发表时间：
1989-12-01
影响因子：
11.1
通讯作者：
LACKS, SA
中科院分区：
文献类型：
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作者：
CERRITELLI, S;SPRINGHORN, SS;LACKS, SA
纯化由Dpn II限制性基因盒编码的两种DNA-腺嘌呤甲基化酶，并在各种DNA底物上比较它们的活性。DpnA能够甲基化单链DNA和双链DNA，而DpnM仅甲基化双链DNA。虽然这两种酶都作用于DNA中的5 "-GATC-3"，但DpnA也可以甲基化鸟嘌呤位置改变的序列，但速率较低。构建dpnA基因中的缺失突变并转移至染色体。通过甲基化和未甲基化质粒的转化途径，以dpnA突变体和野生型受体的传输进行了检查。突变体细胞比野生型细胞更强烈地限制未甲基化供体质粒的建立。在野生型中，通过转化途径进入的供体质粒DNA的单链在质粒转化为双链形式之前明显被Dpn A甲基化，其中质粒将对Dpn II内切核酸酶敏感。因此，DpnA的生物学功能可能是增强质粒转移至含Dpn II的肺炎链球菌菌株。
The two DNA-adenine methylases encoded by the Dpn II restriction gene cassette were purified, and their activities were compared on various DNA substrates. DpnA was able to methylate single-strand DNA and double-strand DNA, whereas DpnM methylated only double-strand DNA. Although both enzymes act at 5''-GATC-3'' in DNA, DpnA can also methylate sequences altered in the guanine position, but at a lower rate. A deletion mutation in the dpnA gene was constructed and transferred to the chromosome. Transmission by way of the transformation pathway of methylated and unmethylated plasmids to dpnA mutant and wild-type recipients was examined. The mutant cells restricted unmethylated donor plasmid establishment much more strongly than did wild-type cells. In the wild type, the single strands of donor plasmid DNA that enter by the transformation pathway are apparently methylated by DpnA prior to conversion of the plasmid to a double-strand form, in which the plasmid would be susceptible to the Dpn II endonuclease. The biological function of DpnA may, therefore, be the enhancement of plasmid transfer to Dpn II-containing strains of Streptococcus pneumoniae.