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CXXC zinc finger domain This domain contains eight conserved cysteine residues that bind to two zinc ions. The CXXC domain is found in a variety of chromatin-associated proteins. This domain binds to nonmethyl-CpG dinucleotides. The domain is characterized by two repeats, and shows a peculiar internal duplication in which the second unit is inserted into the first one. Each of these units is characterized by four conserved cysteines, displaying a CXXCXXCX(n)C motif that chelate a Zn+2 ion. The DNA binding interface has been identified by NMR. In eukaryotes, the CXXC domain is found in stramenopiles, plants and metazoans. Plants possess a mono-CXXC domain that is present in distinct chromatin proteins. Structural comparisons show that the mono-CXXC is homologous to the structural-zinc binding domain of medium chain dehydrogenases.
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