Structural and Functional Peculiarities of α-Crystallin

α-Crystallin is the major protein of the eye lens and a member of the family of small heat-shock proteins. Its concentration in the human eye lens is extremely high (about 450 mg/mL). Three-dimensional structure of native α-crystallin is unknown. First of all, this is the result of the highly heterogeneous nature of α-crystallin, which hampers obtaining it in a crystalline form. The modeling based on the electron microscopy (EM) analysis of α-crystallin preparations shows that the main population of the α-crystallin polydisperse complex is represented by oligomeric particles of rounded, slightly ellipsoidal shape with the diameter of about 13.5 nm. These complexes have molecular mass of about 700 kDa. In our opinion, the heterogeneity of the α-crystallin complex makes it impossible to obtain a reliable 3D model. In the literature, there is evidence of an enhanced chaperone function of α-crystallin during its dissociation into smaller components. This may indirectly indicate that the formation of heterogeneous complexes is probably necessary to preserve α-crystallin in a state inactive before stressful conditions. Then, not only the heterogeneity of the α-crystallin complex is an ev