α B - Crystallin - coated MAP microtubule resists nocodazole and calcium - induced disassembly

one of the small heat-shock proteins (sHSPs), is constitutively expressed in heart, skeletal muscle, kidney and brain (Dubin et al., 1989), as well as in lens. It has an approximate molecular mass of 22 kDa and exists as a large, oligomeric complex of approximately 200-800 kDa in the native state (Bloemendal, 1977). The complex is composed of a globular oligomer, and denatured proteins bind to the molecular surface (Haley et al., 1998) and the central region of the complex (Boyle and Takemoto, 1994). The structure of αB-crystallin is thought to have three domains – the N-terminal hydrophobic domain, the conserved C-terminal 'α-crystallin domain' and an exposed, flexible C-terminal extension (Quax-Jeuken et al., 1985). In lens, αB-crystallin prevents other lens crystallins from ultraviolet-induced aggregation (Lee et al., 1998), suggesting that αB-crystallin might provide lens transparency. However, the function of αB-crystallin in nonlenticular tissues is unknown. There are some tissues in which the expression level of αB-crystallin is higher in unstressed conditions than those of heat-shocked NIH3T3 cells (Klemenz et al., 1993), so αB-crystallin might have a special role in these tissues. It has been reported that αB-crystallin is involved in the stabilization and the regulation of cytoskeletal proteins, such as actin in C6