Probable core component of multiple cullin-RING-based BC3B (BTB-CUL3-BTB) E3 ubiquitin-protein ligase complexes which mediate the ubiquitination and subsequent proteasomal degradation of target proteins. As a scaffold protein may contribute to catalysis through positioning of the substrate and the ubiquitin-conjugating enzyme. The functional specificity of the BC3B complex depends on the substrate recognition component (By similarity). Involved in ubiquitin-mediated degradation of btb3. Protein modification; protein ubiquitination. Probable component of multiple cullin-RING-based BC3B (BTB-CUL3-BTB) E3 ubiquitin-protein ligase complexes formed by cul-3, rbx-1 and a variable BTB domain-containing protein as adapter and substrate recognition component (By similarity). Interacts with btb1, btb2, btb3, nedd8 and pip1. Neddylated; enhancing the ubiquitin-ligase activity. Belongs to the cullin family.