We have designed novel multinuclear metal-binding sites by introducing 96 Cys residues at the 2-fold symmetric interfaces in the protein cage of fenitin. X-ray crystal structure analysis showed that the introduced Cys coordinates to Au ions, forming a multinuclear gold-binding site. This study revealed that the robust cage structure contributes to fix the Cys residues introduced at the desired position and the ferritin subunit interface is a suitable site for constructing multinuclear metal-binding architectures.