Component of the sarcoglycan complex, a subcomplex of the dystrophin-glycoprotein complex which forms a link between the F-actin cytoskeleton and the extracellular matrix. Interacts with FLNC (By similarity). Cross-link to form 2 major subcomplexes: one consisting of SGCB, SGCD and SGCG and the other consisting of SGCB and SGCD. The association between SGCB and SGCG is particularly strong while SGCA is loosely associated with the other sarcoglycans. Interacts with DAG1. Most strongly expressed in skeletal and heart muscle. Also detected in proliferating myoblasts. Disulfide bonds are present. Belongs to the sarcoglycan beta/delta/gamma/zeta family.