KITE proteins: new insights to evolution and dynamics of SMC complexes

We described marked structural similarities between prokaryotic SMC/ScpAB, MukBEF and eukaryotic SMC5/6 complexes (Palecek and Gruber, Structure, 2015). They posses short kleisin molecules while condensin and cohesin complexes contain long kleisins. All kleisins bind SMC proteins through their conserved N- and C-terminal domains while their different middle regions associate with different types of subunits: short kleisins interact with KITE (Kleisin-Interacting Tandem winged-helix Element) and long klesins interact with HAWK (HEAT Associated With Kleisin) proteins. The presence of KITE proteins in prokaryotic SMC/ScpAB and eukaryotic SMC5/6 complexes suggests their close evolutionary relation and an evolutionary path from prokaryotic to eukaryotic SMC complexes via SMC5/6-like ancestors. Different structural features of the KITE and HAWK proteins suggest different regulation and mechanics of their respective SMC complexes. We will show KITE structural elements and their dynamic properties that might be involved in shaping of the kleisin molecules. We will propose a new KITE role in regulation of prokaryotic SMC/ScpAB and eukaryotic SMC5/6 complexes.