Heat shock protein beta-8 (HSPB8, also HSP22 or CRYAC) is a 22-25kD member of the small HSP (HSP20) family of proteins. It is expressed in muscle (smooth, skeletal and cardiac), and serves as a molecular chaperone. Human HSPB8 contains one α-crystalline domain (aa 93-170) that mediates protein-protein interaction, and N- plus C-terminal flanking sequences that generate homodimers, homooligomers, and heterodimers with HSP27 and HSPB7. Phosphorylation at Ser57 blocks HSPB8 chaperone activity. Human HSPB8 shares 94% aa identity with both mouse and canine HSPB8. Deficiencies in HSPB8 are involved in distal motor neuropathy type 11A.