CADMIUM-BINDING PROTEIN IN ROOTS OF MAIZE

A partially purified Cd binding protein was isolated from roots of maize (Z. mays L.). Proteins were first separated on the anion exchanger QAE-Sephadex A-25. The major Cd fraction, comprising as much as 85% of the buffer-soluble Cd, was then chromatographed on Sephadex G-75 in 1 M KCl buffer. The resulting partially purified protein preparation was dark brown, had an apparent MW of 3100, and bound 2 g atoms Cd/mol. The cysteine content was 40%; the Cd:cysteine ratio was 1:6. The Cd-thiolate chromophore was evident from spectroscopic measurements. The roots produced the metallothioneinlike protein after they were exposed to 3 .mu.M Cd for 4 days.