Metal-Thiolate Clusters in the C-Terminal Domain of Human Neuronal Growth Inhibitory Factor (GIF)

Abstract

: Neuronal growth inhibitory factor (GIF), a metallothionein-like protein (metallothionein-3), impairs the survival and neurite formation of cultured neurons. Native GIF contains 4 Cu(I) and three Zn(II) ions organized in homometallic metal-thiolate clusters. However, the cluster localization is not known. In this study, the metal-thiolate clusters formed with monovalent and divalent metal ions in the C-terminal domain of human GIF [GIF(32-68)] containing 11 cysteines were investigated. The cluster formation was followed by using electronic absorption, circular dichroism (CD), and magnetic circular dichroism (MCD) spectroscopy, and in the case of Cu(I) complexes also by luminescence spectroscopy at 77 K. Spectroscopic studies on the Cu(I)-GIF(32-68) complexes showed the successive formation of two air-sensitive Cu 4 S 8-9 - and Cu 6 S 11 -clusters. With Zn(II) and Cd(II) ions, a well-defined M 4 S 11 -cluster is formed in which each metal ion is tetrahedrally coordinated by cy..