Alpha-A-crystallin (also known as Alpha-crystallin A subunit or Heat shock protein beta-4) (αA-crystallin or HSPB4)

Alpha-A-crystallin is a small heat shock protein that comprises approximately 40% of the dry weight of the mammalian eye lens and exists in a 3:1 ratio with alpha-B-crystallin. This 19.8 kDa protein functions as a molecular chaperone, binding to misfolded and denatured proteins to prevent their aggregation and precipitation, which would otherwise cause lens opacity and cataract formation. Alpha-A-crystallin is composed of 173 amino acids organized predominantly in beta-sheet structures, with a conserved alpha-crystallin domain (~90 amino acids) flanked by variable N-terminal and C-terminal regions. The protein's chaperone activity is central to maintaining lens transparency throughout life, as it suppresses the formation of light-scattering protein complexes under a range of physiological and stress conditions including elevated temperature, oxidative stress, and pH changes. While not a classical drug target, alpha-A-crystallin has been intensively studied for over 50 years because therapeutic strategies aimed at preserving or enhancing its chaperone function could potentially prevent or delay cataract formation, the leading cause of blindness worldwide.

Other names

Alpha crystallin subunit AHeat shock protein beta-4 (HSPB4)Lens alpha-A crystallinSmall heat shock protein alpha-A

Chaperone-mediated prevention of protein aggregation through binding to unfolded or denatured proteins\nSuppression of light-scattering aggregates that cause lens opacity\nStabilization of other crystallins (beta and gamma crystallins) under denaturing and physiological conditions