HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Vats, N. Articles by Lee, S. F. Search for Related Content PubMed PubMed Citation Articles by Vats, N. Articles by Lee, S. F. Agricola Articles by Vats, N. Articles by Lee, S. F.

Characterization of a copper-transport operon, copYAZ, from Streptococcus mutans

Department of Microbiology and Immunology, Faculty of Medicine¹, and Department of Applied Oral Sciences, Faculty of Dentistry², Dalhousie University, Halifax, Nova Scotia, CanadaB3H 3J5

Author for correspondence: Song F. Lee (Applied Oral Sciences). Tel: +1 902 494 8799. Fax: +1 902 494 6621. e-mail: Song.Lee{at}Dal.Ca

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. Strep. mutans wild-type cells were resistant to 800 µM Cu²⁺, whereas cells of a cop knock-out mutant were killed by 200 µM 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⁺.

Keywords: copper transport, copper resistance, P-type ATPase, heavy metals

Abbreviations: CAT, chloramphenicol acetyltransferase; THA, Todd–Hewitt agar; THB, Todd–Hewitt broth; TYG, tryptone/yeast extract glucose broth

The GenBank accession number for the cop operon sequence reported in this paper is AF296446.

This article has been cited by other articles:

				H. Hasman The tcrB gene is part of the tcrYAZB operon conferring copper resistance in Enterococcus faecium and Enterococcus faecalis Microbiology, September 1, 2005; 151(9): 3019 - 3025. [Abstract] [Full Text] [PDF]

				C. Y. Loo, K. Mitrakul, I. B. Voss, C. V. Hughes, and N. Ganeshkumar Involvement of the adc Operon and Manganese Homeostasis in Streptococcus gordonii Biofilm Formation J. Bacteriol., May 1, 2003; 185(9): 2887 - 2900. [Abstract] [Full Text] [PDF]

				V. Adaikkalam and S. Swarup 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 Microbiology, September 1, 2002; 148(9): 2857 - 2867. [Abstract] [Full Text] [PDF]