Beta S-crystallin Research Articles

Calf lens alpha-crystallin, a molecular chaperone, builds stable complexes with beta s- and gamma-crystallins.

Calf water-soluble (WS) crystallins consist of high-molecular weight (HM), alpha-, beta H-, beta L-, beta s- and gamma-crystallins. alpha-Crystallin as a molecular chaperone forms a structure with a central hole, known as Carver's model. The only crystallins fitting into this central cavity are beta s- and gamma-crystallins, with native molecular weights of 28 and 18.5-21 kD, respectively. The beta s-crystallin is loosely bound to this structure, whereas with the application of 7M urea in the sample, beta s-, may be some beta L-components and all gamma-crystallins emerge from the central hole. Although WS and water-insoluble (WI) crystallins display the same immunologic determinants, there is an appreciable difference in electrophoretic mobility already in the young calf lens. alpha-Crystallins from the WI part demonstrate a clear cathodic shift. WI beta- and gamma-crystallins show smaller but well perceptible cathodic shifts. The chaperone function of alpha-crystallin preserves the original structures of beta s- and gamma-crystallins for aggregation and other influences.

Primary structure of beta s-crystallin from human lens.

The complete primary structure of beta s-crystallin from human lens is reported. The sequence was elucidated by automatic Edman degradation of tryptic and CNBr peptides. The blocked N-terminal dipeptide was identified by fast-atom-bombardment mass spectroscopy. The sequence comparison with other members of crystallin family reveals a closer relationship to human gamma-crystallin (53% identity) than with beta A3/A1 crystallin (37% identity). The structure, evolutionary characteristics and role of beta s-crystallin in lens are discussed.

Molecular organization and structural stability of .beta.s-crystallin from calf lens

beta s-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% alpha-helix, 45% beta-sheet, 12% bends, and 27% remainders. This result indicates that the structural organization of beta s-crystallin is reasonably similar to that of other beta and gamma family members. A comparison assessed between beta s- and gamma 2-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 beta s-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 pH and guanidine hydrochloride, on the conformational behavior of beta s has also been evaluated by numerous spectroscopic techniques. The range of pH stability was between 6.5 and 8.(ABSTRACT TRUNCATED AT 250 WORDS)

Protein distribution patterns in concentric layers from single bovine lenses: changes with development and ageing.

Protein distribution patterns were determined in concentric layers removed from 24 bovine lenses ranging in age from about 6 months before birth to 180 months post-natal. It was possible to distinguish alterations in protein synthesis patterns during development and changes due to ageing, i.e., prolonged existence of the proteins. It was found that alpha-crystallin represents a constant 50% of the proteins synthesized by the fibre cells throughout life. However, the protein becomes progressively less soluble with increasing age. Beta-crystallin synthesis increases from 30% of the total proteins during prenatal development to around 40% in post-natal fibre cells. This increase is due to increased production of the beta-crystallin. In old tissues, beta H-crystallin is converted to a high molecular weight from (HMW beta) gamma-crystallins account for 22% of the proteins synthesized in the earliest prenatal fibre cells. This level decreases rapidly through prenatal development until they represent about 4% of the total at birth. Beta S-crystallin synthesis commences around this time and in the post-natal fibre cells is essentially the only low molecular weight protein. The possible significance of some of these changes is discussed with regard to the functional requirements of the lens.

Superior resolution of γ-crystallins from microdissected eye lens by cation-exchange high-performance liquid chromatography

A novel procedure is presented for the rapid quantitative analysis of eye lens gamma-crystallins and beta s-crystallin by ion-exchange high-performance liquid chromatography on Synchropak CM300. At least six different gamma-crystallin gene products can be resolved from the soluble fraction of calf lens extract. This method is applicable to the analysis of microsections from individual lenses, and can be used to rapidly characterize spatial variations in gamma-crystallin composition which occur with aging and cataractogenesis.