InterPro domain: IPR044925

His-Me finger is a diverse superfamily of endonuclease proteins present in all forms of life and involved in various cellular processes. The structural core of this group of proteins consists of a beta-hairpin followed by an alpha-helix, forming a binding site for a single catalytic metal ion. The His-Me finger is thought to be suited for efficient, nonspecific DNA cleavage. The term 'His-Me' refers to a nearly invariant catalytic histidine (His) residue and a bound metal ion (Me). His-Me finger-containing proteins are commonly called HNH nucleases. HNH sequence motif consists of the central, nearly invariant, catalytic histidine at the C terminus of the first beta-strand (HNH), an asparagine (HNH) in the extensive loop connecting the two beta-strands known as the omega-loop (16)-and a histidine (HNH) in the core alpha-helix. This second histidine is often substituted by an asparagine, which, in most cases, is the only residue that directly binds the metal ion [ 1 ].

1. Systematic classification of the His-Me finger superfamily. Nucleic Acids Res 45, 11479-11494