Substrate-recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex. Required for muscle atrophy following denervation. Protein modification; protein ubiquitination. Part of a SCF (SKP1-cullin-F-box) protein ligase complex. Interacts with SKP1, CUL1 and RBX1/ROC1 (By similarity). Auto-ubiquitinated. May be neddylated. Neddylation may be required for E3 ligase activity (By similarity).