Effective display of metallothionein tandem repeats on the bioadsorption of cadmium ion |
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Authors: | Kouichi Kuroda Mitsuyoshi Ueda |
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Institution: | (1) Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan |
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Abstract: | To increase the level of adsorption of heavy metal ions in surface-engineered yeasts, a yeast metallothionein (YMT) was tandemly
fused and displayed by means of an α-agglutinin-based display system. The display of the YMT and its tandem repeats was examined
by immunofluorescent labeling. The adsorption and recovery of Cd2+ on the cell surface was increasingly enhanced with increasing number of tandem repeats. All Cd2+-binding sites in the YMT tandem repeats were suggested to be completely occupied. To investigate the relationship between
cell-surface adsorption and protection against heavy metal ion toxicity, the tolerance of these surface-engineered yeasts
to Cd2+ was examined by growing in Cd2+-containing liquid medium. The rate of growth was found to be dependent on the number of displayed tandem repeats of YMT.
These results suggest that the characteristics of surface-engineered yeasts as a bioadsorbent were dependent on the ability
of the displayed proteins to bind metal ions, and the adsorption of heavy metal ions on the cell surface plays a major role
in the ability of the cells to resist the toxic effects of metal ions. |
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