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Helicobacter pylori cad A encodes an essential Cd(II)–Zn(II)–Co(II) resistance factor influencing urease activity
Author(s) -
Herrmann Lutz,
Schwan Dorothee,
Garner Rachel,
Mobley Harry L.T.,
Haas Rainer,
Schäfer Klaus P.,
Melchers Klaus
Publication year - 1999
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1999.01496.x
Subject(s) - urease , helicobacter pylori , biology , complementation , mutant , microbiology and biotechnology , escherichia coli , plasmid , enzyme , bacteria , heterologous expression , gene , biochemistry , recombinant dna , genetics
Inactivation of Helicobacter pylori cad A, encoding a putative transition metal ATPase, was only possible in one of four natural competent H. pylori strains, designated 69A. All tested cad A mutants showed increased growth sensitivity to Cd(II) and Zn(II). In addition, some of them showed both reduced 63 Ni accumulation during growth and no or impaired urease activity, which was not due to lack of urease enzyme subunits. Gene complementation experiments with plasmid (pY178)‐derived H. pylori cad A failed to correct the deficiencies, whereas resistance to Cd(II) and Zn(II) was restored. Moreover, pY178 conferred increased Co(II) resistance to both the cad A mutants and the wild‐type strain 69A. Heterologous expression of H. pylori cad A in an Escherichia coli znt A mutant resulted in an elevated resistance to Cd(II) and Zn(II). Expression of cad A in E. coli SE5000 harbouring H. pylori nixA , which encodes a divalent cation importer along with the H. pylori urease gene cluster, led to about a threefold increase in urease activity compared with E. coli control cells lacking the H. pylori cad A gene. These results suggest that H. pylori Cad A is an essential resistance pump with ion specificity towards Cd(II), Zn(II) and Co(II). They also point to a possible role of H. pylori CadA in high‐level activity of H. pylori urease, an enzyme sensitive to a variety of metal ions.