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. Up-regulated in denervated muscles (at protein level), with highest expression levels around 14 days following denervation. Negatively regulated by the bone morphogenetic protein (BMP) pathway. Auto-ubiquitinated. May be neddylated. Neddylation may be required for E3 ligase activity, since it was observed only after purification with o-phenanthroline (PubMed:24076600). Truncated N-terminus.