Lens crystallins

Abraham, E.C., Swarmy, M.S. and Perry, R.E. (1989). Non-enzymatic glycation of lens crystallins in diabetes and ageing. Prog. Clin. Biol. Res. 304, 123-139. 

The frequency of the amide I peak observed in the lens is sensitive to protein secondary structure. From its absolute position at 1672 cm-1, which is indicative for an antiparallel pleated 3-sheet structure, and the absence of lines in the 1630-1654 cm-1 region, which would be indicative of parallel (1-sheet and a-helix structures, the authors could conclude that the lens proteins are all organized in an antiparallel, pleated 3-sheet structure [3]. Schachar and Solin [4] reached the same conclusion for the protein structure by measuring the amide I band depolarization ratios of lens crystallins in excised bovine lenses. Later, the Raman-deduced protein structure findings of these two groups were confirmed by x-ray crystallography. 

Lack of congruence of sequence and structure with function Common sequence and structure, indeed identity of the protein itself, do not imply a unique function Each pair, o-succinylbenzoate synthase (OSBS)-N-acetylamino acid racemase, and lens crystallin-lactate dehydrogenase, share sequence and structure but differ in function. 

Although nonenzymatic glycosylation may affect practically every protein in vivo, it is likely that nonenzymatic browning will occur only in proteins that have a slow turnover or none at all, such as lens crystallins, collagen, elastin and proteoglycans. In some tissues, these proteins are, in effect, "stored" for a lifetime and undergo some characteristic changes, many of which have been observed in stored and processed foodstuffs (Table II). 

R.H. Nagaraj and V.M. Monnier, Isolation and characterization of a blue fluorophore from human eye lens crystallins in vitro formation from Maillard reaction with ascorbate and ribose, Biochim. Biophys. Acta, 1992, 1116, 34-42. 

T.J. Lyons, G. Silvestri, J.A. Dunn, D.G. Dyer, and J.W. Baynes, Role of glycation in modification of lens crystallins in diabetic and non-diabetic senile cataracts, Diabetes, 1991, 40, 1010-1015. 

Figure 7.9. Thermal stabilities of eye lens crystallins of differently thermally adapted vertebrates. The temperature (°C) at which 50% loss of secondary structure occurred, as measured using CD spectroscopy, is given as a function of the maximal body temperature of each species. Species (1) Pagothenia borchgrevinki (Antarctic fish), (2) Coryphaenoides armatus (deep-sea fish), (3) Coryphaen-oides rupestris (deep-sea fish),...

Identification of Lens Crystallins A Model System for Gene Recruitment... 

The most important part of the search for sequence relationships is the completeness of the database. Early in the discovery that taxon-specific crystallins were related to enzymes, no relatives of relationship between yeast argininosuccinate lyase (ASL) and chicken lens -crystallins was seen. In fact, the yeast ASL sequence was published on the same day as a personal database the sequence of human ASL, which was just being published.28 There is no substitute for complete and up-to-date databases. 

Jaenicke, R, (1996) Stability and folding of ultrastable proteins eye lens crystallins and enzymes from thermophiles, FASEB J. 10, 84-92. 

One of us (J.C.) has undertaken a systematic NMR study of eye lens crystallin proteins. Much of this work has been summarized in two recent review articles63 64 and will not be repeated here. Suffice to say that the mammalian... 

Piatigorsky, J. (1992). Lens crystallins. Innovation associated with changes in gene regulation. Journal of Biological Chemistry, 267, 4277-80. 

Stevens, V. J., Rouzer, C. A., Monnier, V. M., and Cerami, A., Diabetic cataract formation Potential role of glycosylation of lens crystallins. Proc. Natl. Acad. Sci U.SA. 75,2918-2922 (1978). 

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