This is the C-terminal hood domain found in Heterocyst differentiation control protein (HetR). HetR-C binds to PatS peptide. Two PatS6 peptides bind to the lateral clefts of HetR-Hood domain, and trigger significant conformational changes of the flap domain, resulting in dissociation of the auxiliary alpha-helix and eventually release of HetR from the DNA major grove and termination of transcription [1].

1: Structural insights into HetR-PatS interaction involved in cyanobacterial pattern formation. Hu HX, Jiang YL, Zhao MX, Cai K, Liu S, Wen B, Lv P, Zhang Y, Peng J, Zhong H, Yu HM, Ren YM, Zhang Z, Tian C, Wu Q, Oliveberg M, Zhang CC, Chen Y, Zhou CZ; Sci Rep. 2015;5:16470. PMID:26576507