BINDING OF COPPER, CADMIUM, ZINC, AND MANGANESE IN PROTEINS OF AQUATIC MACROPHYTES

Gel filtration and atomic absorption analysis were used to investigate binding of metals by proteins in the freshwater moss Vesicularia dubyana and the marine algae Ulva lactuca and Gracilaria verrucosa in the norm and after 24-h incubation in a medium with Cu and Cd concentration of 0.3 mg.liter-1. The effect of a surplus of Cu and Cd on the content of Zn, Fe, and Mn in proteins was also studied. Metals are detected for the most part in proteins isolated during initial extraction with 0.02 M Tris-HCl buffer (pH 8.6) in V. dubyana, but in proteins extracted with the buffer after membrane destruction caused by treating the biomass with acetone in the algae. Accumulation of Cu and Cd in proteins on the whole is nonspecific and inversely proportional to protein molecular weight. The concentration of Zn, Fe, and Mn in proteins declines under the influence of Cd. The presence of Mn in proteins lowers binding of Cu in them. The existence of specific metallothionein-like proteins that bind Cu and Cd is possible in V. dubyana.