title: Reduction of Hg2+ with reduced mammalian cytochrome c by cytochrome c oxidase purified from a mercury-resistant acidithiobacillus ferrooxidans strain, MON-1.
abstract: Acidithiobacillus ferrooxidans AP19-3, ATCC 23270, and MON-1 are mercury-sensitive, moderately mercury-resistant, and highly mercury-resistant strains respectively. It is known that 2,3,5,6-tetramethyl-p-phenylendiamine (TMPD) and reduced cytochrome c are used as electron donors specific for cytochrome c oxidase. Resting cells of strain MON-1 had TMPD oxidase activity and volatilized metal mercury with TMPD as an electron donor. Cytochrome c oxidase purified from strain MON-1 reduced mercuric ions to metalic mercury with reduced mammalian cytochrome c as well as TMPD. These mercury volatilization activities with reduced cytochrome c and TMPD were completely inhibited by 1 mM NaCN. These results indicate that cytochrome c oxidase is involved in mercury reduction in A. ferrooxidans cells. The cytochrome c oxidase activities of strains AP19-3 and ATCC 23270 were completely inhibited by 1 muM and 5 muM of mercuric chloride respectively. In contrast, the activity of strain MON-1 was inhibited 33% by 5 muM, and 70% by 10 muM of mercuric chloride, suggesting that the levels of mercury resistance in A. ferrooxidans strains correspond well with the levels of mercury resistance of cytochrome c oxidase.
authors.affiliation: Division of Bioscience, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan. sugio@cc.okayama-u.ac.jp
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Sugio
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Fujii
authors.forename: Yumika
authors.initials: Y
authors.lastname: Ninomiya
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Kanao
authors.forename: Atsunori
authors.initials: A
authors.lastname: Negishi
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Takeuchi
mesh_terms: D042763:Acidithiobacillus / Q000201:enzymology*; D000818:Animals; D045304:Cytochromes c / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D003576:Electron Transport Complex IV / Q000378:metabolism*; D008628:Mercury / Q000737:chemistry / Q000494:pharmacology*; D010084:Oxidation-Reduction
chemical_list: D045304:Cytochromes c; D003576:Electron Transport Complex IV; D008628:Mercury