Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin ligase complex required for translational homeostasis. The BCR(KLHL25) ubiquitin ligase complex acts by mediating ubiquitination of hypophosphorylated eif4ebp1 (4E-BP1) (By similarity). Protein modification; protein ubiquitination. Component of the BCR(KLHL25) E3 ubiquitin ligase complex, at least composed of cul3, klhl25 and rbx1.