Nat. Struct. Biol. 9, 833–838 (2002).

In this paper we concluded that the SET domain structure contains a 'knot' with the description: “... the knot involves the insertion of the C-terminal strand β22 threading through a hoop consisting of the two strands, β19 and β20, and their connecting region.” We did not explicitly state that part of the hoop is connected through hydrogen bonds, and the knot in our structure does not conform to the strictest definition of a protein knot. Nevertheless, the knotted structure may be alternatively described as a threaded-loop structure. A recent publication (W.R. Taylor et al. Computational Biol. Chem. 27, 11–15; 2003) fully addresses these topological issues in the context of SET proteins.