Adapter protein that binds to and probably organizes the subcellular localization of a variety of membrane proteins. May link various receptors to the actin cytoskeleton and the extracellular matrix via the dystrophin glycoprotein complex. Plays an important role in synapse formation and in the organization of UTRN and acetylcholine receptors at the neuromuscular synapse. Binds to phosphatidylinositol 4,5-bisphosphate (By similarity). Monomer and homodimer. Interacts with the other members of the syntrophin family SNTB1 and SNTB2; SGCG and SGCA of the dystrophin glycoprotein complex; NOS1; GRB2; the sodium channel proteins SCN4A and SCN5A; F-actin and calmodulin (By similarity). Interacts with dystrophin protein DMD and related proteins DTNA and UTRN and with MAPK12, TGFA and GA. Interacts with MYOC; regulates muscle hypertrophy (By similarity). Interacts with DTNB (By similarity). In skeletal muscle, it localizes at the cytoplasmic side of the sarcolemmal membrane and at neuromuscular junctions. High expression in skeletal muscle and heart. Low expression in brain, pancreas, liver, kidney and lung. Not detected in placenta. The PH 1 domain mediates the oligomerization in a calcium dependent manner, and the association with the phosphatidylinositol 4,5-bisphosphate. The PDZ domain binds to the last three or four amino acids of ion channels and receptor proteins. The association with dystrophin or related proteins probably leaves the PDZ domain available to recruit proteins to the membrane (By similarity). The SU domain binds calmodulin in a calcium-dependent manner. Phosphorylated by CaM-kinase II. Phosphorylation may inhibit the interaction with DMD (By similarity). The disease is caused by variants affecting the gene represented in this entry. Belongs to the syntrophin family.