refractive increments of lens proteins (original) (raw)
Physical-chemical studies on bovine eye lens proteins
Experimental Eye Research, 1982
Low molecular weight a-crystallins, isolated from adult and embryonic bovine lenses, have been characterized using physical-chemical methods. From light-scattering measurements and from the Svedberg relation, a molecular weight of 785000 + 30000 can be concluded. From hydrodynamic data, namely the sedimentation coefficient, the translational diffusion coefficient, the intrinsic viscosity and the rotational diffusion coefficient, a symmetric shape of the molecules in solution with a rather high hydration can be concluded. The low-molecular a-crystallins, isolated from the cortex of adult lenses and from embryonic lenses, have identical hydrodynamic parameters.
A comparative study of vertebrate eye lens crystallins using isoelectric focusing and densitometry
Comparative biochemistry and physiology. B, Comparative biochemistry, 1993
1. The crystallin proteins of numerous species belonging to different classes of vertebrates have been studied. 2. Species-specific crystallin patterns are revealed which unequivocally characterize the different species. 3. A marked variability in the number and percentage of alpha-, beta- and gamma-crystallins were found in the various species. 4. The gamma-crystallin family, with a meagre number of common bands, has proved to be most representative of the species. The beta-crystallins, with their greater number of common bands, have been best preserved throughout vertebrate evolution. 5. From the similarity coefficient matrix a dendrogram is drawn up, a visual phylogenetic summary of the interrelationships between the vertebrates considered. 6. In the Discussion, other aspects are considered, such as lens morphology, functionality, animal age, post-synthetic modifications and genetic factors.
Experimental Eye Research, 1984
The aL of cortical and nuclear fiber cells have been studied using hydrodynamical and physicochemical techniques. From the sedimentation and the diffusion coefficients in identical conditions, it can be concluded that aL.n is appreciably larger than aL.c but both have a similar structure in solution: a spherical particle with a high hydration. The aL N not only contains several degraded aA-and aB-peptides but also a typical pattern of j%peptides. The fluorescence spectrum indicates a shift of the hydrophobic tryptophan residues from a hydrophobic environment in aLc to a more solvent-exposed and polar neighbourhood for aL N. Also solubility studies on aLc and aL,N in different solvent conditions and temperatures, indicate more apolar interactions between the peptides of the nuclear aL, than its cortical counterpart. The more hydrophobic interaction pattern of the peptides in aL,N can also be reconciled with a lower mean hydration potential, indicative of a higher hydrophobicity of the degraded aA-peptides.
new method for studying lens protein changes
Human lenses can be separated into concentric layers by dissolution and the fates of various lens constituents in such layers can be studied with appropriately sensitive techniques. These techniques have been applied in a study of the ageing of lens proteins. It was found that insoluble protein increases with progression from periphery to lens centre. This increase is more marked in older lenses. Analysis of soluble protein using High Performance Liquid Chromatography shows that the proportion of a-crystallin decreases towards the centre of the lens, and that this decrease becomes greater with age. j3-Crystallins maintain a constant proportion except in inner layers of older lenses. y-Crystallins show a slight decrease in content from periphery to centre. With cataract formation ageing changes are exaggerated.
Journal of Biological Chemistry, 2011
To elucidate the morphological and cellular changes due to introduction of a charge during development and the possible mechanism that underlies cataract development in humans as a consequence of an additional charge, we generated a transgenic mouse model mimicking deamidation of Asn at position 101. The mouse model expresses a human ␣A-crystallin gene in which Asn-101 was replaced with Asp, which is referred to as ␣AN101D-transgene and is considered to be "deamidated" in this study. Mice expressing ␣AN101D-transgene are referred to here CRYAA N101D mice. All of the lines showed the expression of ␣AN101D-transgene. Compared with the lenses of mice expressing wild-type (WT) ␣A-transgene (referred to as CRYAA WT mice), the lenses of CRYAA N101D mice showed (a) altered ␣A-crystallin membrane protein (aquaporin-0 (AQP0), a specific lens membrane protein) interaction, (b) extracellular spaces between outer cortical fiber cells, (c) attenuated denucleation during confocal microscopic examination, (d) disrupted normal fiber cell organization and structure during scanning electron microscopic examination, (e) distorted posterior suture lines by bright field microscopy, and (f) development of a mild anterior lens opacity in the superior cortical region during the optical coherence tomography scan analysis. Relative to lenses with WT ␣A-crystallin, the lenses containing the deamidated ␣A-crystallin also showed an aggregation of ␣A-crystallin and a higher level of water-insoluble proteins, suggesting that the morphological and cellular changes in these lenses are due to the N101D mutation. This study provides evidence for the first time that expression of deamidated ␣A-crystallin caused disruption of fiber cell structural integrity, protein aggregation, insolubilization, and mild cortical lens opacity.
Classification of Rat Lens Crystallins and Identification of Proteins Encoded by Rat Lens mRNA
European Journal of Biochemistry, 2005
Endogenous rat lens crystallins have been separated by gel filtration into four fractions, a, fiH, Br. and 7-crystallin. Elution patterns of soluble lens proteins from animals of different ages show a relative decrease of /?H and ;-crystallin during aging. Conversely the relative amounts of r and jL-crystallin are enhanced. The rat crystallin subunits from the four fractions were characterized by one-dimensional and two-dimensional gel electrophoretic techniques. From the results a classification could be derived and a nomenclature for the soluble rat lens proteins is proposed. The products synthesized by rat lens mRNAs in a heterologous cell-free system have also been characterized. Co-electrophoresis of the radioactive products synthesized de novo together with the isolated unlabeled protein fractions on two-dimensional gels shows the relation between primary gene products and their posttranslationally modified derivatives.
Molecular organization and structural stability of .beta.s-crystallin from calf lens
Biochemistry, 1990
&-Crystallin has been purified to homogeneity. Its structural features and conformational behavior have been studied in solution. Protein secondary structure was estimated by curve fitting of far-UV circular dichroism spectra, which gave 16% a-helix, 45% P-sheet, 12% bends, and 27% remainders. This result indicates that the structural organization of &-crystallin is reasonably similar to that of other p and 7 family members. A comparison assessed between &and 7,-crystallin by the use of predictive methods (flexibility and volume plots) reveals that the two proteins differ in respect to their local flexibility and packing, although they show similar overall organization. The interdomain and the C-terminal regions were found to be more flexible in &-crystallin. This finding can be explained by the presence of smaller amino acid residues within these structural districts. The location of one out of four tryptophans, i.e., Trp-162, in a flexible and exposed region of the protein was found to be the origin of the fluorescence heterogeneity. In fact, the fluorescence emission maximum of the native protein, centered at 328 nm, is due to two emitting centers, whose emission maxima are located at 323 and 330 nm, respectively, as evidenced by acrylamide quenching of fluorescence. The effect of perturbing agents, such as p H and guanidine hydrochloride, on the conformational behavior of p, has also been evaluated by numerous spectroscopic techniques. The range of pH stability was between 6.5 and 8. Above this interval, a conformational change takes place. In the acid region, the protein is unstable and precipitates irreversibly. The conformational resistance to guanidine hydrochloride has also been shown to be weak. GdnHCl denaturation curves were neither superimposable nor ascribable to a very cooperative transition. This result suggests a non-two-state denaturation equilibrium reflecting the presence of structural domains. The main conclusion of our work is that the protein shows a very narrow range of stability. This result indicates that an inherent structural stability may not be a general property of lens proteins. Therefore, the evolutive hypothesis about a specific recruitment of stable proteins in the lens architecture may need reconsideration.
Ubiquitous Lens α-, β-, and γ-Crystallins Accumulate in Anuran Cornea as Corneal Crystallins
Journal of Biological Chemistry, 2007
Corneal epithelium is known to have high levels of some metabolic enzymes such as aldehyde dehydrogenase in mammals, gelsolin in zebrafish, and ␣-enolase in several species. Analogous to lens crystallins, these enzymes and proteins are referred to as corneal crystallins, although their precise function is not established in any species. Although it is known that after lentectomy, the outer cornea undergoes transdifferentiation to regenerate a lens only in anuran amphibians, major proteins expressed in an anuran cornea have not been identified. This study therefore aimed to identify the major corneal proteins in the Indian toad (Bufo melanostictus) and the Indian frog (Rana tigrina). Soluble proteins of toad and frog corneas were resolved on two-dimensional gels and identified by matrix-assisted laser desorption ionization time-of-flight/time-of-flight and electrospray ionization quadrupole time-of-flight. We report that anuran cornea is made up of the full complement of ubiquitous lens ␣-, -, and ␥-crystallins, mainly localized in the corneal epithelium. In addition, some taxon-specific lens crystallins and novel proteins, such as ␣or -enolase/-crystallin, were also identified. Our data present a unique case of the anuran cornea where the same crystallins are used in the lens and in the cornea, thus supporting the earlier idea that crystallins are essential for the visual functions of the cornea as they perform for the lens. High levels of lens ␣-, -, and ␥-crystallins have not been reported in the cornea of any species studied so far and may offer a possible explanation for their inability to regenerate a lens after lentectomy. Our data that anuran cornea has an abundant quantity of almost all the lens crystallins are consistent with its ability to form a lens, and this connection is worthy of further studies.