Characterization of a copper-transport operon, copYAZ, from Streptococcus mutans.
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 (CXCX(4)CXC) 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. Strep. mutans wild-type cells were resistant to 800 microM Cu2+, whereas cells of a cop knock-out mutant were killed by 200 microM 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+.
Department of Microbiology and Immunology, Faculty of Medicine1, and Department of Applied Oral Sciences, Faculty of Dentistry2, Dalhousie University, Halifax, Nova Scotia, CanadaB3H 3J5.
Neeraj
N
Vats
Department of Microbiology and Immunology, Faculty of Medicine1, and Department of Applied Oral Sciences, Faculty of Dentistry2, Dalhousie University, Halifax, Nova Scotia, CanadaB3H 3J5.
Song F
SF
Lee
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D003300:Copper / Q000378:metabolism* / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009876:Operon; D017422:Sequence Analysis, DNA; D013295:Streptococcus mutans / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D003300:Copper