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J.Health Sci., 52(4), 475-477, 2006
Involvement of Aromatic Amino Acids in Phenylmercury Transport by MerT Protein
Takeshi Nagata, Masako Kiyono,1
and Hidemitsu Pan-Hou*
Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotogecho, Hirakata, Osaka 573-0101, Japan
To investigate the role of aromatic amino acids of MerT protein in phenylmercury transport, two merT variants (pMRTm1P and pMRTm2P) with specific site-directed mutations were constructed and examined their effects on C6H5Hg+-transport. Substitution of Phe-36 and Trp-40 residues located on the periplasmic loop of MerT in turn with Ala and Val, respectively, did not affect the Hg2+-uptake, but caused a significant reduction in the C6H5Hg+-uptake by bacterial cells with intact merT gene. Introduction of specific mutations changing Phe-108, 114, 115 to Ala, and Tyr-110, 116 to Ser in the C-terminal region of the third transmembrane of MerT also caused large reduction in the uptake of C6H5Hg+, but had no effect on the Hg2+-uptake. In addition, both mutations caused a significant reduction in the hypersensitivity to C6H5Hg+, but without affecting the Hg2+-hypersensitive phenotype. Together these results suggest that the aromatic amino acids of MerT protein may play an important role in the transport of C6H5Hg+ across the cell membrane.
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