Characterization of a cadmium-binding complex of cabbage leaves

• Published in: Plant physiology (Bethesda) Vol. 76; no. 3; pp. 797 - 805
• Main Author: Wagner, G.J
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.11.1984
• Subjects: Adducts; Agronomy. Soil science and plant productions; Amino acids; Analytical, structural and metabolic biochemistry; Animals; BINDING; Biological and medical sciences; Brassica capitate; CABBAGES; CADMIUM; cadmium-binding protein; Chemical constitution; Economic plant physiology; Electrophoresis; Fundamental and applied biological sciences. Psychology; Gels; LEAVES; Ligands; Liver; Plants; Protein hormones. Growth factors. Cytokines; Proteins; Cadmium; Binding protein; Vegetals; Cruciferae; Dicotyledones; Angiospermae; Spermatophyta; Metal; Physicochemical properties
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.76.3.797

The chemical nature of a principal, inducible cadmium-binding complex which accumulates in cabbage leaves (Wagner and Trotter 1982 Plant Physiol 69: 804-809) was studied and compared with that of animal metallothionein and copper-binding proteins isolated from various organisms. The apparent molecular weight of native cabbage complex and carboxymethylated ligand of the complex under native conditions as determined by gel filtration was about 10,000 daltons. Under denaturing conditions their apparent molecular weights were about 2000 daltons. Ligand of native complex contained 37, 28, and 9 residue per cent of glutamic acid-glutamine, cysteine, and glycine, respectively, and low aromatic residue, serine and lysine content. The high acidic and low hydrophobic residue content explain the behavior of complex on electrophoresis in the presence and absence of sodium dodecyl sulfate. Its isoelectric point was below 4.0 and it bound 4 to 6 moles cadmium per mole ligand in what appear to be cadmium-mercaptide chromophores. The complex was found to be heat stable, relatively protease insensitive, and lacking in disulfide bonds. Attempts to determine the primary sequence of reduced native complex and carboxymethylated, cleaved ligand using the Edman degradation procedure were unsuccessful. An electrophoretic procedure is described for preparative isolation of purified complex and a method is described for monitoring ligand of complex as its fluorescent dibromobimane adduct.