Key assembly factor of SCF (SKP1-CUL1-F-box protein) E3 ubiquitin ligase complexes that promotes the exchange of the substrate-recognition F-box subunit in SCF complexes, thereby playing a key role in the cellular repertoire of SCF complexes. Acts as a F-box protein exchange factor (Probable). No visible phenotype. Cells lacking both RUB1 and CAND1 show defects in morphological, growth and protein degradation, consistent with a reduction in SCF ubiquitin ligase activity. Belongs to the CAND family.