Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin-protein ligase complex required for mitotic progression and cytokinesis (PubMed:23213400). The BCR(KLHL18) E3 ubiquitin ligase complex mediates the ubiquitination of AURKA leading to its activation at the centrosome which is required for initiating mitotic entry (PubMed:23213400). Regulates light-and dark-dependent alpha-transducin localization changes in rod photoreceptors through UNC119 ubiquitination and degradation (By similarity). Preferentially ubiquitinates the unphosphorylated form of UNC119 over the phosphorylated form (By similarity). In the presence of UNC119, under dark-adapted conditions alpha-transducin mislocalizes from the outer segment to the inner part of rod photoreceptors which leads to decreased photoreceptor damage caused by light (By similarity).