= SET domain
{c}
A <SET domain> is a <protein domain> found in many <methyltransferases> that modify <lysine> residues in <histones> and other <proteins>. It contributes to the catalytic machinery that transfers a <methyl group> to a selected target. The domain's presence suggests a family relationship, but does not by itself specify which residue a particular <enzyme> modifies.
In 2000, experiments on SUV39H1 and related <proteins> identified <histone H3> <lysine> 9 methylation activity. Mutational and biochemical analysis localized the catalytic requirement to the <SET domain> together with adjacent cysteine-rich regions.<Regulation of chromatin structure by site-specific histone H3 methyltransferases by S. Rea and others>[Abstract: H3 lysine 9 specificity, SET dependence and adjacent regions]{ref} This linked a recognizable sequence region to a concrete chemical reaction on <chromatin>, while also showing why isolating a domain name from its surrounding structure can oversimplify enzyme function.
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