Alpha-crystallins, composed of alphaA (~19kD) and alphaB (~19.2kD) subunits, are major water-soluble proteins accounting for almost 50% of total protein in the mammalian transparent eye lens and they are also found in a variety of other tissues (1). The two other crystallin families, beta and gama, are homologous to each other but not to the alpha family or the sHspis. Alpha-crystallins are also referred to as small heat shock proteins, since they are induced by increased temperature in a variety of organisms (2). The alpha-crystallins have sequence homology as well as structural and functional similarities with the small Hspis such as Hsp25/27 (3). Most alpha-crystallins have four common structural and functional features: (i) molecular weight between 12 and 43kD, (ii) the formation of large oligomeric complexes composed of alphaA-crystallin, alphaB-crystallin and Hsp25/27, (iii) the moderately conserved alpha-crystallin domain in the central region of the protein, and (iv) molecular chaperone activity (2,4). The alpha-crystallin domain, comprised of approximately 90 residues, is bound by variable N-terminal and C-terminal extensions and is involved in oligomer assembly. Oligomers can reach 800kD or more and are dynamic, exhibiting subunit exchanges and organizational plasticity, possibly leading to functional diversity. Phosphorylation of serine residues occurs during development and in response to stress, and usually decreases oligomer size (4). Chaperone activity requires, and is modulated by, oligomerization and is limited to binding unfolded intermediates to prevent irreversible aggregation (2,4). Although productive release and refolding of denatured proteins requires close cooperation with other chaperones. Other proposed functions include a role in membrane stabilization (2) and modulation of intermediate filament organization during physiological stress and neurodegenerative disease (5). Source: Bovine eye lens Molecular Weight: 20,037 (Approximate) Applications: On a 15-well minigel system, 100ng of protein/lane should be sufficient when used in a colorimetric Western Blot. Other applications not tested. Storage and Stability: Aliquot to avoid repeated freezing and thawing and store at -70C. Aliquots are stable for 6 months after receipt. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.
