Alpha crystallin domain (ACD) found in mammalian HspB3, also known as heat-shock protein 27-like protein (HSPL27, 17-kDa) and similar proteins. sHsps are molecular chaperones that suppress protein aggregation and protect against cell stress, and are generally active as large oligomers consisting of multiple subunits. HspB3 is expressed in adult skeletal muscle, smooth muscle, and heart, and in several other fetal tissues. In muscle cells HspB3 forms an oligomeric 150 kDa complex with myotonic dystrophy protein kinase-binding protein (MKBP/ HspB2), this complex may comprise one of two independent muscle-cell specific chaperone systems. The expression of HspB3 is induced during muscle differentiation controlled by the myogenic factor MyoD. HspB3 may also interact with Hsp22 (HspB8).