The Reaction of EDTA With Metallothionein and its Separate Clusters: Complex Kinetic Behavior With Novel Protein Concentration Dependence

Mammalian metallothionein (MT) is Involved in the detoxiflcation of Cd(ll) ions. It binds 7 Cd(ll) in two Cd-thiolate clusters (Cd4S11 and C3S9) which are located in two protein domains. 111Cd and 2-D NMR studies show that in lobster, two Cd3S9 domains exist. Despite homologies in the location of cysteines between the corresponding domains of the lobster and mammalian MTs (8 of the 9 cysteines in each domain), the sequence specific Cd-thiolate connections differ in both domains of the lobster protein. To see if these differences alter the chemistry of the proteins, two reactions related to the function of the protein were compared.