This domain is found in the catalytic core RABEX-5 present in Homo sapiens. RABEX, also known as Rab GTPase exchange factors, regulate endocytic trafficking through activation of the Rab families RAB5, RAB21 and RAB22. The domain is helical in nature [1].

1: Structural basis for Rab GTPase activation by VPS9 domain exchange factors. Delprato A, Lambright DG; Nat Struct Mol Biol. 2007;14:406-412. PMID:17450153