This domain is found in many archaeal proteins, including HVO_2753 (also known as Small CPxCG-related zinc finger protein) from Haloferax volcanii [1]. NMR 3D structure analysis revealed the content of four C(P)XCG motifs, suggesting the presence of two zinc-binding pockets (ZBPs). However, only C(P)XCG motifs 2 and 4 (comprising Cys-32 to Cys-35 and Cys-50 to Cys-53) form a ZBP and binds one zinc atom, while C(P)XCG motifs 1 and 3 (comprising Cys-12 to Cys-15 and Cys-39 to Cys-42) form a four-Cys cluster that do not bind zinc. The four C(P)XCG motifs are critical for protein stability, folding and functionality [1]. This domain can also be present in small zinc finger proteins from bacteria and eukaryotes.

1: Biological functions, genetic and biochemical characterization, and NMR structure determination of the small zinc finger protein HVO_2753 from Haloferax volcanii. Zahn S, Kubatova N, Pyper DJ, Cassidy L, Saxena K, Tholey A, Schwalbe H, Soppa J; FEBS J. 2020; [Epub ahead of print] PMID:32905660