 Deep trefoil knots have been found in the SPOUT superfamily.including methyltransferase proteins involved in posttranscriptional RNA modification in all three Domains of Life, including bacterium "Thermus thermophilus" and proteins, in archaea and in eukaryota.In many cases the trefoil knot is part of the active site or a ligand-binding site and is critical to the activity of the enzyme in which it appears.