SET domains are protein lysine methyltransferase enzymes. SET domains appear to be protein-protein interaction domains. A subset of SET domains have been called PR domains. The SET domain consists of two regions known as N-SET and SET-C. SET-C forms an unusual and conserved knot-like structure of probably functional importance. Additionally to SET-N and SET-C, an insert region (SET-I) and flanking regions of high structural variability form part of the overall structure [2]. This domain is found in fungi associated with SET and N-SET domains.

1: Structure of the SET domain histone lysine methyltransferase Clr4. Min J, Zhang X, Cheng X, Grewal SI, Xu RM; Nat Struct Biol 2002;0:0-0. PMID:12389037

2: Structure of SET domain proteins: a new twist on histone methylation. Marmorstein R; Trends Biochem Sci 2003;28:59-62. PMID:12575990