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 and DAG1. 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 (By similarity). Most strongly expressed in skeletal and heart muscle. Also detected in stomach and uterus muscle. Disulfide bonds are present. Defects in SGCD are the cause of cardiomyopathy, an autosomal recessive disease which is characterized by progressive myocardial necrosis and heart failure leading to premature death. A large portion of the 5'-end of the gene, including the first exon, is deleted and an alternative promoter and first exon are used. Belongs to the sarcoglycan beta/delta/gamma/zeta family.