Su(ar)3-9 proteins attach methyl groups to the histone labeled H3 at its ninth amino acid residue, which is a lysine.

• 9蛋白将甲基加在组蛋白H3的第九位氨基酸残基，也就是赖氨酸残基上，从而使H3组蛋白贴上了个标签。