ubstrate-specific adapter of a BCR (BTB-CUL3-RBX1) E3 ubiquitin ligase complex (By similarity). Required for skeletal muscle development (PubMed:23746549). Component of the BCR(KLHL40) E3 ubiquitin ligase complex. Expressed in skeletal muscle and heart. Detected, although at much lower levels, in brain, eye and fin. At 16 and 24 hpf, restricted to muscle precursor cells in somites. Also detected at 48 hpf. Morpholino knockdown of the protein results in a curved trunk and small head at 48 hpf. Morphants show disruption of skeletal muscle patterning with an irregular, wavy appearance of the striated myofibers and extensive gaps between the myofibers. Myofibers show disorganized and irregular patterns with small aggregates of alpha-actinin, suggesting nemaline bodies. Animals exhibit sporadic muscle tremor and coordinated swimming is not observed. Belongs to the KLHL40 family.