Characterization of a copper-transport operon, copYAZ, from Streptococcus mutans
Characterization of a copper-transport operon, copYAZ, from Streptococcus mutans
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DOI：
10.1099/00221287-147-3-653
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发表时间：
2001-03-01
期刊：
影响因子：
--
通讯作者：
Lee, SF
中科院分区：
文献类型：
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作者：
Vats, N;Lee, SF
从口腔细菌变形链球菌JH1005中克隆了一个铜转运（copYAZ）操纵子。DNA测序结果表明，该操纵子包含三个基因（copY、copA和copZ），它们的两侧分别有一个启动子和一个与因子无关的终止子。copy编码了一个147aa的小蛋白，在c端有一个重金属结合基序（CXCX4CXC）。与其他细菌负转录调控因子具有广泛的同源性。copA编码的742 aa蛋白与p型atp酶具有广泛的同源性。copZ编码一个67aa蛋白，该蛋白在n端也含有一个重金属结合基序（CXXC）。Northern印迹显示Cu2+诱导链球菌产生了3.2 kb的转录本。突变细胞，表明这些基因是作为一个多顺反子信息合成的。对cop操纵子的转录起始位点进行了定位，发现它位于启动子-操作子区域的反向重复序列中。表带。突变体野生型细胞对800 muM Cu2+具有抗性，而cop敲除突变体的细胞被200 muM Cu2+杀死。将cop敲除突变体与cop操纵子互补后，Cu2+抗性恢复到野生型水平。野生型和突变体对其他重金属的敏感性没有任何差异，这表明该操纵子对铜是特异性的。利用氯霉素乙酰转移酶报告基因融合，发现cop操纵子可被CopY负调控，并可被Cu2+抑制。
A copper-transport (copYAZ) operon was cloned from the oral bacterium Streptococcus mutans JH1005. DNA sequencing showed that the operon contained three genes (copY, copA and copZ), which were flanked by a single promoter and a factor-independent terminator. copy encoded a small protein of 147 aa with a heavy-metal-binding motif (CXCX4CXC) at the C-terminus. CopY Shared extensive homology with other bacterial negative transcriptional regulators. copA encoded a 742 aa protein that shared extensive homology with P-type ATPases. copZ encoded a 67 aa protein that also contained a heavy-metal-binding motif (CXXC) at the N-terminus. Northern blotting showed that a 3.2 kb transcript was produced by Cu2+-induced Strep. mutans cells, suggesting that the genes were synthesized as a polycistronic message. The transcriptional start site of the cop operon was mapped and shown to lie within the inverted repeats of the promoter-operator region. Strap. mutans wild-type cells were resistant to 800 muM Cu2+, whereas cells of a cop knock-out mutant were killed by 200 muM Cu2+. Complementation of the cop knock-out mutant with the cop operon restored Cu2+ resistance to wild-type level. The wild-type and the mutant did not show any differences in susceptibility to other heavy metals, suggesting that the operon was specific for copper. By using a chloramphenicol acetyltransferase reporter gene fusion, the cop operon was shown to be negatively regulated by CopY and could be derepressed by Cu2+.