<p> Members of this family encode protein methylase activity. The enzyme activity has been mapped to the SET domain and the adjacent cysteine-rich regions. The SET domain was originally identified in Su(var)3-9, E(z) and Trithorax genes in <taxon tax_id="7227">Drosophila melanogaster</taxon> (Fruit fly). The sequence conservation pattern and structure analysis of the SET domain provides clues regarding the possible active site residues of the domain. There are three conserved sequence motifs in most of the SET domains. The N-terminal motif (I) has characteristic glycines. The central motif (II) has a distinct pattern of polar and charged residues (Asn, His). The C-terminal conserved motif (III) has a characteristic dyad of polar residues. It has been shown that deregulated SUV39H1 (the human ortholog) interferes at multiple levels with mammalian higher-order chromatin organisation and these properties depend primarily on the SET domain. </p> Histone H3-K9 methyltransferase