This is the N-terminal domain of human co-chaperone protein HscB (hHscB). This domain is capable of binding a metal ion through its tetracysteine metal binding motif. The metal atom is coordinated by a set of four cysteine residues (Cys41, Cys44, Cys58 and Cys61) on opposed beta-hairpins. Although the N-domain lacks any recognizable secondary structure elements, it has several distant structural homologs including C-4 zinc finger domains and rubredoxin [1].

1: Structure of human J-type co-chaperone HscB reveals a tetracysteine metal-binding domain. Bitto E, Bingman CA, Bittova L, Kondrashov DA, Bannen RM, Fox BG, Markley JL, Phillips GN Jr; J Biol Chem. 2008;283:30184-30192. PMID:18713742