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J.Health Sci., 56(1), 123-127, 2010
Roles Played by MerE and MerT in the Transport of Inorganic and Organic Mercury Compounds in Gram-negative Bacteria
Yuka Sone,a Hidemitsu Pan-Hou,b
Ryosuke Nakamura,a Kou Sakabe,a, c
and Masako Kiyono*, a
aDepartment of Public Health and Molecular Toxicology, School of Pharmacy, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan,
bFaculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan and
cDepartment of Human Structure and Function, Tokai University School of Medicine, 143 Shimokasuya, Isehara, Kanagawa 259-1193, Japan
In order to clarify the physiological roles played by MerP, MerT and MerE in Gram-negative bacteria, we constructed the plasmids pTP4 and pTPE21, which contained the genes merR, merT and merP, from the Pseudomonas K-62 plasmid pMR26, or the same genes with the merE gene of Tn21 from the Shigella flexneri plasmid NR1 (R100), respectively. Cells containing pTP4 showed increased hypersensitivity to Hg(II), but maintained a normal sensitivity to CH3Hg(I). However, cells with pTPE21 exhibited increased hypersensitivity to Hg(II) and CH3Hg(I). Cells with pTP4 accumulated appreciably more Hg(II) than control cells, but no significant difference was observed in their uptake of 14CH3Hg(I). In contrast, the cells containing pTPE21 accumulated significantly larger amounts of Hg(II) and 14CH3Hg(I) than either control cells or cells with pTP4. These results suggest that the mer operons have evolved to redirect uptake of mercurials into dedicated, specific and relatively high-affinity transport systems comprising the small periplasmic protein MerP and two inner membrane proteins, MerT and MerE.
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