Effective display of metallothionein tandem repeats on the bioadsorption of cadmium ion.
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 alpha-agglutinin-based display system. The display of the YMT and its tandem repeats was examined by immunofluorescent labeling. The adsorption and recovery of Cd(2+) on the cell surface was increasingly enhanced with increasing number of tandem repeats. All Cd(2+)-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 Cd(2+) was examined by growing in Cd(2+)-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.
Kuroda
Kouichi
K
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Japan.
Ueda
Mitsuyoshi
M
D000327:Adsorption; D002104:Cadmium / Q000737:chemistry*; D008668:Metallothionein / Q000235:genetics*; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D020080:Tandem Repeat Sequences
D002104:Cadmium; D008668:Metallothionein