Characterization of a copper-transport operon, copYAZ, from Streptococcus mutans The GenBank accession number for the cop operon sequence reported in this paper is AF296446.

Abstract

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 heavymetal-binding motif (CXXC) at the N-terminus. Northern blotting showed that a 32 kb transcript was produced by Cu 2M -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 µM Cu 2M , whereas cells of a cop knock-out mutant were killed by 200 µM Cu 2M . Complementation of the cop knock-out mutant with the cop operon restored Cu 2M 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 Cu 2M .

Inactivation by Hg2+ and methylmercury of the glutamine/amino acid transporter (ASCT2) reconstituted in liposomes: Prediction of the involvement of a CXXC motif by homology modelling

“…The residues Cys-207 and Cys-210, which belong to a CXXC metal binding motif, are located at the end of a large hydrophilic loop of the transporter. The transport protein may have a trimeric form as described for the Glt ph [42], with a concave aqueous basin in the middle facing towards the extracellular side (Fig. 8 B).…”

“…8 B). Interestingly, ASCT2 contains a CXXC motif which is typical of metal binding sites in proteins [42]. The two cys residues (Cys-207 and Cys-210) of the motif, highlighted in dark grey (Fig.…”

Molecular characterization of an operon, cueAR, encoding a putative P1-type ATPase and a MerR-type regulatory protein involved in copper homeostasis in Pseudomonas putida The GenBank accession number for the sequence reported in this paper is AF390440.

“…(Bayle et al, 1998) and the atkYB operon of Lactobacillus sakei (Stentz et al, 2000), do not have MerR-type helix-turnhelix regulators. In the cueAR region, a homologue of the recently published Streptococcus copZ regulator (Vats & Lee, 2001), copP, is present. However, the threegene operon in Streptococcus, namely copYAZ, encodes a regulator similar to that encoded by the copYZAB copper-transport system of Enterococcus -this regulator is not of the MerR type.…”

Global transcriptional analysis of acid-inducible genes in Streptococcus mutans: multiple two-component systems involved in acid adaptation

“…However, using transcriptional reporter gene fusions to the promoter of the atp operon, Quivey and colleagues found that the increase in F 1 F 0 -H/ATPase activity was correlated with increased transcription of the atp operon of S. mutans grown at low pH (Kuhnert et al, 2004 (Kakinuma, 1998;Magalhaes et al, 2005). For instance, the copYAZ operon in S. mutans encodes a Ptype ATPase responsible for transport of copper, allowing this organism to tolerate the high concentrations of copper potentially released from dental amalgam (Vats & Lee, 2001). pacL (SMU.1563), together with two other genes, SMU.1561 and SMU.1562, at the same locus, encodes a Ptype potassium transporter system.…”