The Cd-binding protein from tomato compared to those of other vascular plants.
Cd-binding protein from tomato roots was partially purified and characterized. The Cd-protein complex was eluted as a single Cd peak from QAE-Sephadex A-25 and purified further on Sephadex G-75 in 1 M KC1 buffer. Circular dichroism measurements showed positive Cotton bands at 232 and 273 nm and a negative band at 253 nm, indicative of Cd-thiolate coordination. The major amino acids were Cys (25.6%), Glx (53.3%), Asx (5.4%) and Gly (12.8%) with no aromatic residues detected. The Cd:Cys ratio was 1:2.4. The material had an apparent molecular mass of 3,000 daltons on gel filtration through Sephadex G-50 fine in 1 M KC1 buffer. The tomato protein resembled the Cd-binding proteins isolated from black bentgrass, maize and cabbage. The presence of Cd-thiolate coordination and the high content of Cys are critical features typical of metallothioneins. The abundance of Glx creates a highly anionic protein which is unlike animal metallothioneins. It is proposed that the Cd-binding proteins from vascular plants be designated phytometallothioneins.
D000596:Amino Acids / Q000032:analysis; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D002942:Circular Dichroism; D004591:Electrophoresis, Polyacrylamide Gel; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008668:Metallothionein / Q000032:analysis*; D008970:Molecular Weight; D009994:Osmolar Concentration; D010944:Plants / Q000032:analysis*; D011489:Protein Denaturation
D000596:Amino Acids; C004203:cadmium-binding protein; D008668:Metallothionein