refractive increments of lens proteins (original) (raw)
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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.
Biochemical and Biophysical Research Communications, 1970
The vertebrate lens is composed of two distinct cell types, the epithelial cell and the fiber cell. ol-Crystallin, a structural protein found in both cell types, is composed of four subunits @Ai, olA2, aB1, and olB2). In the epithelial cells the cr-crystallin consists mainly of crA2 and crB2 with trace amounts of crA1 and cyB1. In the fiber cell there is a large increase in the amount of c~A1 and olBl subunits. This quantitative increase in two specific subunits is related to the process of cellular growth and differentiation in the vertebrate lens.
Biochemical and Biophysical Research Communications, 1974
incorporation of ~3H3 leucine into ollgomeric a-crystallin via individual subunits has beenmeasured in epithelial cells and cortex fiber cells from adult bovine lenses in vitro. Our data show that the ratio of [3H~ leucine incorporation via subunlts aB2 and aA 2 Ts shifted from a value of about 1:2 in epithelial cells to a value of about 1:3 in fiber cells. Thus, in this system, cellular differentiation is accompanied by a change in the stolchiometry of assembly of individual subunits to form the oligomerlc a-crystallin molecule. These results indicate possible changes in the rates of synthesis of individual a-crystallln subunits. a-Crystallin is an ollgomerlc structural protein that is found in both epithelial cells and fiber cells of the bovine lens (1) and has a molecular weight of approximately 1 X 106 (2, 3). Treatment with urea and mercaptoethanol dissociates the oligomer into its polypeptide subunits, all of which have single molecular weights of about 25,000 (4). These subunits can be resolved into two acidic proteins (aA 1 and aA2) , which have isoelectric points of 5.6 and 5.9, respectively, and two basic proteins (aB 1 and aB2) , which have isoelectric points *Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation.
Primary sequence contribution to the optical function of the eye lens
Scientific Reports, 2014
The crystallins have relatively high refractive increments compared to other proteins. The Greek key motif in bc-crystallins was compared with that in other proteins, using predictive analysis from a protein database, to see whether this may be related to the refractive increment. Crystallins with Greek keys motifs have significantly higher refractive increments and more salt bridges than other proteins with Greek key domains. Specific amino acid substitutions: lysine and glutamic acid residues are replaced by arginine and aspartic acid, respectively as refractive increment increases. These trends are also seen in S-crystallins suggesting that the primary sequence of crystallins may be specifically enriched with amino acids with appropriate values of refractive increment to meet optical requirements. Comparison of crystallins from five species: two aquatic and three terrestrial shows that the lysine/arginine correlation with refractive increment occurs in all species investigated. This may be linked with formation and maintenance of salt bridges.
Primary sequence contribution to optical function of the eye lens
The crystallins have relatively high refractive increments compared to other proteins. The Greek key motif in bc-crystallins was compared with that in other proteins, using predictive analysis from a protein database, to see whether this may be related to the refractive increment. Crystallins with Greek keys motifs have significantly higher refractive increments and more salt bridges than other proteins with Greek key domains. Specific amino acid substitutions: lysine and glutamic acid residues are replaced by arginine and aspartic acid, respectively as refractive increment increases. These trends are also seen in S-crystallins suggesting that the primary sequence of crystallins may be specifically enriched with amino acids with appropriate values of refractive increment to meet optical requirements. Comparison of crystallins from five species: two aquatic and three terrestrial shows that the lysine/arginine correlation with refractive increment occurs in all species investigated. This may be linked with formation and maintenance of salt bridges.