Vestergaard Mun'delanji, Matsumoto Sachiko, Nishikori Shingo, Shiraki Kentaro, Hirata Kazumasa, Takagi Masahiro
School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa, Japan.
Anal Sci. 2008 Feb;24(2):277-81. doi: 10.2116/analsci.24.277.
The interactions between Cd(2+) and the C-terminal region of phytochelatin (PC) synthase using recombinant wild-type and mutant PC synthase were studied. We show that site-directed mutagenesis of Cys residues at C(358)C(359)XXXC(363)XXC(366) motif decreases the number of Cd(2+) and other heavy metal ions interacting with the enzyme, and that the motif binds the metals discriminatingly. The optimum binding ratio of PC synthase to Cd(2+) was also determined. The findings indicate that Cys exists as a free SH residue and that it is involved in the regulation of PC enzyme activity by transferring the metals into closer proximity with the catalytic domain. These results are important in understanding heavy metal detoxification mechanisms in higher plants, a step towards phytoremediated-applications.
利用重组野生型和突变型植物螯合肽（PC）合酶，研究了Cd(2+)与植物螯合肽合酶C端区域之间的相互作用。我们发现，对C(358)C(359)XXXC(363)XXC(366)基序处的半胱氨酸残基进行定点诱变，会减少与该酶相互作用的Cd(2+)和其他重金属离子的数量，并且该基序能选择性地结合金属。还确定了PC合酶与Cd(2+)的最佳结合比例。研究结果表明，半胱氨酸以游离巯基残基的形式存在，并且通过将金属转移至更靠近催化结构域的位置参与PC酶活性的调节。这些结果对于理解高等植物中的重金属解毒机制具有重要意义，是迈向植物修复应用的重要一步。
