Structural basis of eye lens transparency: light scattering by concentrated solutions of bovine alpha-crystallin proteins

Abstract

Short range order of the crystallins does account for the transparency of the eye lens. To explain the solution structure of this highly concentrated protein solution on a quantitative basis, the hydrodynamic structure and the interparticle interactions of the proteins have to be known. For that purpose, the light scattering of concentrated solutions of alpha-crystallin has been studied. Starting from the detailed knowledge of the solution parameters of alpha-crystallin in diluted solutions, the structure of concentrated solutions up to 360 mg/ml has been studied using light scattering. Our results indicate that subtle changes in the macromolecular structure such as optical anisotropy or structural asymmetry for part of the alpha-crystallins, which results in solute light-scattering heterogeneity, can dramatically increase the light scattering by the alpha-crystallins and cause solution opacity.

Crystal structures of truncated alphaA and alphaB crystallins reveal structural mechanisms of polydispersity important for eye lens function

“…[42][43][44][45][46][47] Much study has been devoted to understanding how the lens remains transparent, despite its high protein concentratons. [42][43][44][45][46][47][48] One factor is avoidance of phase separations within the lens, which would lead to light scattering and opacity, as in cataract formation. The common types of phase separation in protein solutions at high concentration are protein crystal formation and protein aggregation.…”

“…42,43,[47][48][49]58 Both the AP interface and the C-terminal tail interactions observed for the alpha crystallin family exhibit structural polymorphisms (Fig. 7).…”

Automated measurement of the static light scattering of macromolecular solutions over a broad range of concentrations

“…Although the measurement and analysis of static light scattering of protein solutions has long been a standard method for the characterization of the molar mass and of the self-association of proteins [9], studies of the light scattering of highly concentrated protein solutions [10,11] are quite rare due to technical difficulties associated with sample preparation, conventional techniques of batch measurement, and limitation of conventional analyses to treatment of firstorder deviations from thermodynamic ideality. We have recently presented an extension of multicomponent light scattering theory that is applicable in principle to solutions of multiple species of proteins at arbitrary concentration, taking into account both attractive interactions leading to self-and/or hetero-association, and nonspecific repulsive interactions leading to thermodynamically nonideal behavior [5].…”

Identification of Interaction Sites between Human βA3- and αA/αB-crystallins by Mammalian Two-hybrid and Fluorescence Resonance Energy Transfer Acceptor Photobleaching Methods

“…The ␤-and ␥-crystallins have only structural properties (2-4), except that our results showed that ␤A3 crystallin contains proteinase activity (5, 6). The expressions of the crystallins are both developmentally and spatially regulated (1), and their interactions lead to the transparency of the lens because of short range order of the crystallin matrix (7,8).Previous reports have shown that the ␣-crystallin interacts with other crystallins and intermediate filaments (2). An interaction of ␣-crystallin with ␤L-crystallin produced filament-like structures, and similar interactions between ␤L-crystallin with ␣A-crystallin (isolated from UV-A-irradiated lenses) showed even more pronounced filament formation (9).…”