Functional dissection of a mercuric ion transporter, MerC, from Acidithiobacillus ferrooxidans

Yoshito Sasaki, Takahiro Minakawa, Atushi Miyazaki, Simon Silver, Tomonobu Kusano

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    23 Citations (Scopus)


    Topological analysis with a phoA gene fusion suggested that Acidithiobacillus ferrooxidans MerC, a mercury transporter, has two periplasmic loops and four transmembrane domains. Cys-23 and Cys-26 of the protein were involved in Hg2+-recognition/uptake, but Cys-132 and Cys-137 were not. Escherichia coli cells producing the MerC were hypersensitive to CdCl 2. In this case, mutation of His72 rendered the host cells less CdCl2 sensitive, whereas none of the Cys residues affected it. E. coli cells expressing the gene encoding a mercuric ion transporter (merC)-deletion mutant, in which the coding-sequence of the carboxy-terminal cytoplasmic region was removed, retained Hg2+ hypersensitivity and showed about 55% HgCl2 uptake ability compared to that of the one expressing the intact merC, indicating that the region is not essential for Hg2+ uptake. Coexpression of A. ferrooxidans the gene encoding mercuric reductase (merA) and the merC deletion mutation conferred HgCl 2 tolerance to E. coli host cells. Under this condition, the merC deletion gene product was exclusively present as a monomer.

    Original languageEnglish
    Pages (from-to)1394-1402
    Number of pages9
    JournalBioscience, Biotechnology and Biochemistry
    Issue number7
    Publication statusPublished - 2005


    • Acidithiobacillus ferrooxidans
    • Inorganic mercury
    • MerC
    • Topology
    • Transporter

    ASJC Scopus subject areas

    • Biotechnology
    • Analytical Chemistry
    • Biochemistry
    • Applied Microbiology and Biotechnology
    • Molecular Biology
    • Organic Chemistry


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