查看文章

Mammalian metallothionein-4 (MT-4) was found to be specifically expressed in stratified squamous epithelia where it plays an essential but poorly defined role in regulating zinc or copper metabolism. Here we report on the organization, stability, and the pathway of metal-thiolate cluster assembly in MT-4 reconstituted with Cd²⁺ and Co²⁺ ions. Both the ¹¹³Cd NMR studies of ¹¹³Cd₇MT-4 and the spectroscopic characterization of Co₇MT-4 showed that, similar to the classical MT-1 and MT-2 proteins, metal ions are organized in two independent Cd₄Cys₁₁ and Cd₃Cys₉ clusters with each metal ion tetrahedrally coordinated by terminal and bridging cysteine ligands. Moreover, we have demonstrated that the cluster formation in Cd₇MT-4 is cooperative and sequential, with the Cd₄Cys₁₁ cluster being formed first, and that a distinct single-metal nucleation intermediate Cd₁MT-4 is required in the cluster formation …