Multiple enzyme activities of Escherichia coli MutT protein for sanitization of DNA and RNA precursor pools
Multiple enzyme activities of Escherichia coli MutT protein for sanitization of DNA and RNA precursor pools
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DOI：
10.1021/bi047550k
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发表时间：
2005-05-03
期刊：
影响因子：
2.9
通讯作者：
Ishibashi, T
中科院分区：
文献类型：
--
作者：
Ito, R;Hayakawa, H;Ishibashi, T
8-OxoGua（8-氧代-7，8-二氢鸟嘌呤）在核酸以及细胞的核苷酸库中通过在细胞代谢过程中正常形成的活性氧物质产生。大肠杆菌的MutT蛋白特异性地将含有8-oxoGua的脱氧核糖核苷和核糖核苷三磷酸降解为相应的核苷单磷酸，从而防止8-oxoGua错误掺入DNA和RNA中，这将分别引起突变和表型抑制。在这里，我们报告说，MutT蛋白具有额外的活动，用于清理核苷酸池，以确保准确的DNA复制和转录。它将8-氧代-dGDP水解为8-氧代-dGMP，Km为0.058 μ M，该值显著低于其正常对应物dGDP（170 μ M）。此外，MutT具有将8-氧代-GDP降解为相关核苷单磷酸的活性，其Km值比GDP低8000倍。MutT蛋白的这些多酶活性将促进DNA和RNA合成的高保真度。
8-OxoGua (8-oxo-7,8-dihydroguanine) is produced in nucleic acids as well as in nucleotide pools of cells, by reactive oxygen species normally formed during cellular metabolic processes. MutT protein of Escherichia coli specifically degrades 8-oxoGua-containing deoxyribo- and ribonucleoside triphosphates to corresponding nucleoside monophosphates, thereby preventing misincorporation of 8-oxoGua into DNA and RNA, which would cause mutation and phenotypic suppression, respectively. Here, we report that the MutT protein has additional activities for cleaning up the nucleotide pools to ensure accurate DNA replication and transcription. It hydrolyzes 8-oxo-dGDP to 8-oxo-dGMP with a K-m of 0.058 mu M, a value considerably lower than that for its normal counterpart, dGDP (170 mu M). Furthermore, the MutT possesses an activity to degrade 8-oxo-GDP to the related nucleoside monophosphate, with a K-m value 8000 times lower than that for GDP. These multiple enzyme activities of the MutT protein would facilitate the high fidelity of DNA and RNA syntheses.