A copper-binding protein in root cytoplasm of Polygonum cuspidatum [Polygonaceae] growing in a metalliferous habitat

To investigate the mechanism of Cu tolerance of Polygonum cuspidatum, the Cu-binding protein was isolated from the cytoplasm of the root and rhizome from plants growing in a Cu-contaminated habitat. A Cu-containing compound with a molecular weight of 9,500 was obtained from the cytoplasm of the root and the cortex of the rhizome by Bio-Gel P-30 column chromatography. The amount of this compound increased with increasing Cu content in the cytoplasm. The compound was purified by passage through a DEAE-Cellulofine AL column and further by high performance liquid chromatography. The purified compound was a metallothionein-like protein, because it had high contents of cysteine (31.3%) and acidic amino acids (16.5%) and a very low proportion of aromatic amino acids.