Low molecular weight cadmium-and copper-binding proteins from rat kidneys.

Three isoforms of rat kidney cadmium- and copper-binding proteins [(Cd, Cu)-BP 1, 2, and 3] were isolated. They contained from 75.0 up to 89.0 μg Cd/mg protein, from 7.5 up to 28.0 μg Cu/mg, and from 1.5 up to 12.0 μg Zn/mg protein. Apparent molecular weights of all three isoforms were of about 10,000. Their amino acid compositions were similar to that of rat metallothionein, with cysteine amounting to 25.8-32.7% of all amino acids.