This is a zinc binding motif which contains four cysteine residues which chelate zinc [1]. This domain is often found associated with a Pfam:PF00226 domain. This domain is named after the conserved motif of the final cysteine.

1: Solution structure of Kti11p from Saccharomyces cerevisiae reveals a novel zinc-binding module. Sun J, Zhang J, Wu F, Xu C, Li S, Zhao W, Wu Z, Wu J, Zhou CZ, Shi Y; Biochemistry 2005;44:8801-8809. PMID:15952786