Structural and Functional Peculiarities of alpha-Crystallinстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 4 марта 2022 г.
Аннотация:alpha-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 alpha-crystallin is unknown. First of all, this is the result of the highly heterogeneous nature of alpha-crystallin, which hampers obtaining it in a crystalline form. The modeling based on the electron microscopy (EM) analysis of alpha-crystallin preparations shows that the main population of the alpha-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 alpha-crystallin complex makes it impossible to obtain a reliable 3D model. In the literature, there is evidence of an enhanced chaperone function of alpha-crystallin during its dissociation into smaller components. This may indirectly indicate that the formation of heterogeneous complexes is probably necessary to preserve alpha-crystallin in a state inactive before stressful conditions. Then, not only the heterogeneity of the alpha-crystallin complex is an evolutionary adaptation that protects alpha-crystallin from crystallization but also the enhancement of the function of alpha-crystallin during its dissociation is also an evolutionary acquisition. An analysis of the literature on the study of alpha-crystallin in vitro led us to the assumption that, of the two alpha-crystallin isoforms (alpha A- and alpha B-crystallins), it is alpha A-crystallin that plays the role of a special chaperone for alpha B-crystallin. In addition, our data on X-ray diffraction analysis of alpha-crystallin at the sample concentration of about 170-190 mg/mL allowed us to assume that, at a high concentration, the eye lens alpha-crystallin can be in a gel-like stage. Finally, we conclude that, since all the accumulated data on structural-functional studies of alpha-crystallin were carried out under conditions far from native, they cannot adequately reflect the features of the functioning of alpha-crystallin in vivo.