Metal binding domain of Ada
The Escherichia coli Ada protein repairs O6-methylguanine residues and methyl phosphotriesters in DNA by direct transfer of the methyl group to a cysteine residue. This domain contains four conserved cysteines that form a zinc binding site. One of these cysteines is a methyl group acceptor. The methylated domain can then specifically bind to the ada box on a DNA duplex.