Lead and other metals can substitute for Ca2+ in calmodulin (original) (raw)

1983, Archive Fur Toxikologie

We have studied the interaction between some heavy metal ions, as compared with earth alkali ions, and calmodulin, a tissue protein which binds Ca 2+ and mediates some of its effects. 1. Calmodulin dependent phosphodiesterase was activated with Pb 2+, Ca 2+, Sr 2+, Ba 2 § and Cd 2 § (ECso about 0.8 ~tM). The maximal activation achieved decreases in the order given. Hg 2+, Sn 2+, Fe 2+, Cu 2+, Ni 2 § Bi 3+, and Sb 3+ up to 20 ~tM did not activate. 2. Pb 2+ can replace Ca 2+ with respect to the calmodulin-dependent phosphorylation of brain membranes. With high Pb 2+ concentrations, phosphorylation was inhibited. 3. Calmodulin binding to brain membranes was enhanced with concentrations below 10-4M in the following order: Pb 2+ _-> Ca 2+ ~ Sr 2+ > Cd 2+ > Mn 2+ > Ba 2+. In contrast Mg 2+, Hg 2+, Sn 2+, Fe z+, Ni 2+, Co 2+, and Cu 2+ triggered, if at all, a non-saturable binding of calmodulin. 4. In the flow-dialysis, other ions competed with 45Ca2+ binding to calmodulin in the following order: Pb 2+ -Ca 2+ > Mn 2+, Ba 2+, Cd 2+, Sr 2+.