Two peaks of Cu-containing material were isolated from the soluble cytoplasmic fraction of roots ofAthyrium yokoscense, a fern with a tolerance for heavy metals, by gel filtration on Bio-Gel P-30 and Sephadex G-25. Peak I (apparent molecular weight 9.5 kDa) was only observed in the case of ferns growing on Cu-contaminated soil. Peak II (apparent molecular weight 2 kDa) was found in extracts of ferns from both Cu-contaminated and uncontaminated soil. Peak I was induced in the fern collected from an uncontaminated area by cultivation in Cu-contaminated soil for 14 months. The induced Cu-binding complex present in peak I, therefore, may be involved in mechanisms of Cu-tolerance in the fern. The complex was purified by column chromatography on DEAE-cellulofine and subsequent high-performance liquid chromatography. The purified complex contained a high percentage (26.8) of cysteine, typical of metal-binding peptides from plants.
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