Differential binding of cadmium and copper to the same protein in a heavy metal tolerant species of mayfly ( Baetis thermicus) larvae

Abstract

1. The larvae of mayflies ( Baetis thermicus) that lived in a metal-contaminated river (the river Ashio in Tochigi, Japan) were collected and the concentrations and distributions of several heavy metals in mayflies were compared with those collected from another metal-contaminated river (the river Mazawa in Yamagata, Japan). 2. Distribution profiles of multi-elements in the supernatant of the mayflies were determined simultaneously on a gel filtration column by the HPLC-atomic emission spectrometry method. 3. Sharp cadmium and copper peaks of comparable intensities were observed at slightly different retention times. 4. The copper peak increased at the expense of cadmium peak by stepwise additions in vitro of cupric ions, the replacement being at a molar ratio of Cu/Cd = 5.35. 5. The replacement of cadmium with copper induced shifts of the sulfur and absorbance peaks at 254 and 280 nm to the original copper peak, indicating that cadmium and copper were bound to the same protein separately.