期刊
MICROBIOLOGY-UK
卷 147, 期 -, 页码 653-662出版社
SOC GENERAL MICROBIOLOGY
DOI: 10.1099/00221287-147-3-653
关键词
copper transport; copper resistance; P-type ATPase; heavy metals
类别
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+.
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