Substrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin ligase complex that acts as a key regulator of skeletal muscle development (PubMed:23746549). The BCR(KLHL40) complex acts by mediating ubiquitination and degradation of TFDP1, thereby regulating the activity of the E2F:DP transcription factor complex (By similarity). Promotes stabilization of LMOD3 by acting as a negative regulator of LMOD3 ubiquitination; the molecular process by which it negatively regulates ubiquitination of LMOD3 is however unclear (By similarity). Component of the BCR(KLHL40) E3 ubiquitin ligase complex, at least composed of CUL3, KLHL40 and RBX1. Interacts with LMOD3. Highly expressed in fetal (19, 23 and 31 weeks of gestation) and adult skeletal muscle; expression levels tend to be higher in fetal compared to postnatal muscles (at protein level). Also expressed in fetal and adult heart. The disease is caused by variants affecting the gene represented in this entry. Belongs to the KLHL40 family.