Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin ligase complex that acts as a negative regulator of Wnt signaling pathway and ER-Golgi transport. The BCR(KLHL12) complex is involved in ER-Golgi transport by regulating the size of COPII coats, thereby playing a key role in collagen export, which is required for embryonic stem (ES) cells division (By similarity). Negatively regulates the Wnt signaling pathway, possibly via the targeted ubiquitination and subsequent proteolysis of dvl2 and dvl3 (PubMed:16547521). Regulates convergent-extension movements during early embryonic development (PubMed:16547521). Protein modification; protein ubiquitination. Component of the BCR(KLHL12) E3 ubiquitin ligase complex. Expressed ubiquitously throughout development.