This domain is a long alpha helix, required for interaction with Bcl-x. It is found in BAM, Bim and Bcl2-like protein 11 [1]. This domain is also known as the BH3 domain between residues 146 and 161.

1: The structure of a Bcl-xL/Bim fragment complex: implications for Bim function. Liu X, Dai S, Zhu Y, Marrack P, Kappler JW; Immunity. 2003;19:341-352. PMID:14499110

2: Bcl-2-family proteins: the role of the BH3 domain in apoptosis. Kelekar A, Thompson CB; Trends Cell Biol. 1998;8:324-330. PMID:9704409

3: Role of the BH3 (Bcl-2 homology 3) domain in the regulation of apoptosis and Bcl-2-related proteins. Lutz RJ; Biochem Soc Trans. 2000;28:51-56. PMID:10816098