Kelch repeat and BTB domain-containing protein 13 (KBTBD13)

Kelch repeat and BTB domain-containing protein 13 (KBTBD13) is a muscle-specific actin-binding protein. It is characterized by an N-terminal BTB (Broad complex, Tramtrack, and Bric-à-brac) domain and a C-terminal Kelch-repeat domain that forms a β-propeller structure. KBTBD13 plays a modulatory role in skeletal muscle contraction and relaxation by directly binding to sarcomeric actin filaments, impacting the kinetics and force of muscle contraction. Mutations in KBTBD13 cause Nemaline Myopathy type 6, a dominantly inherited congenital muscle disorder with slow muscle relaxation and structural thin-filament defects. Beyond its actin-binding function, KBTBD13 may act as a substrate adapter for a BTB-CUL3-RBX1 E3 ubiquitin ligase complex, potentially involved in selective protein degradation.

Other names

KBTBD13Kelch repeat and BTB domain-containing protein 13hCG_1645727NEM6Nemaline myopathy type 6HCG1645727kelch repeat and BTB (POZ) domain containing 13

Mutations in KBTBD13 alter actin filament properties—such as stiffness and periodicity—leading to impaired relaxation and decreased muscle contractile force. Putative role in ubiquitination through a BTB-CUL3-RBX1 E3 ligase complex (based on protein domain structure, not directly established).