Cadmium-Phytochelatins From Roots of Wheat Seedlings
GONG Yu-Song, LI Zhen-Guo and YU Shu-Wen(Shanghai Institute of Plant Physiology, Acadmia Sinica, Shanghai 200032)SUN Zhao-Zhi(The Institution of Standard Metrology and Tests, Shanghai Instrumental and Electronic Industry Burean, Shanghai 200031)
A Cd-binding complex (Cd-BC) was isolated and purified from roots of wheat seedlings grown in Hoagland solutions containing CdC1_2 by chromatography with Sephadex G75 and DEAE-cellulose columns. The apparent molecular weight of Cd-BC as determined by gel filtration was about 10 kD, but that by SDSPAGE was very low, as indicated by the fact that the Coomassie brilliant blue R250 stained material was near the electrophoretic front. The Cd-BC showed a shoulder at 255—265 nm in UV absorption spectrum and A_(250)/A_(280)1. The absorption of this shoulder decreased when the sample was acidified and recovered almost entirely after readjustment of pH to 7.5. The amino acid composition of Cd-BC was composed mainly of glutamic acid/glutamine, cysteine and glycine, in a molar ratio of 4:4:1. The results suggest that Cd-BC consist of multiple oligo peptides and be identical with the Cd-phytochelatins (Cd-PCs) formed in other Cd-treated cell suspensions and plants.