Cadmium-binding proteins in Pseudomonas putida: pseudothioneins.

Pseudomonas putida adapted to growth in 3 mM cadmium. The resistance mechanism involved complexation of cadmium in polyphosphate granules, changes in the structure of the cell membrane and induction of three cysteine-rich, low molecular weight proteins (3500-7000) containing 4 to 7 g-atoms per mole of cadmium, zinc, and copper. Each protein was produced during a different phase of growth, and the smallest protein (3500) was released into the environment when the cells lysed at the end of the exponential phase. The metal binding sites of the major protein were further characterized using a range of physical methods, including 113Cd NMR. The properties of the bacterial pseudothioneins are compared to those of metallothioneins.