Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin-protein ligase complex required for synaptic transmission (PubMed:29088697). The BCR(KCTD13) E3 ubiquitin ligase complex mediates the ubiquitination of RHOA, leading to its degradation by the proteasome, thereby regulating the actin cytoskeleton and promoting synaptic transmission (PubMed:29088697). Protein modification; protein ubiquitination. Homotetramer; forms a two-fold symmetric tetramer in solution. Interacts with CUL3; interaction is direct and forms a 5:5 heterodecamer. Component of the BCR(KCTD13) E3 ubiquitin ligase complex, at least composed of CUL3, KCTD13/BACURD1 and RBX1. Interacts with RHOA; with a preference for RhoA-GDP. Interacts with POLD2 and PCNA. Interacts with SPRTN. By TNF-alpha. Reduced synaptic transmission in area CA1 of the hippocampus caused by increased levels of RHOA. Brain size or neural progenitor cell proliferation are not affected. Belongs to the BACURD family. Down-regulation of Kctd13 was initially reported to cause macrocephaly due to increased proliferation (PubMed:22596160). However, it was later shown that deletion of Kctd13 does not cause any change in brain size, embryonic cell proliferation, neurogenesis, or cortical layering/migration (PubMed:29088697). Experimental conditions used may explain discrepancies. A possible explanation being that shRNAs used in the first study, may have affected off-targets.