Keratan sulfate-containing proteoglycans were isolated from bovine cornea (15-month-old to 3-year-old animals) and digested with the enzyme, keratanase II. The released oligosaccharides, which included non-reducing termini and repeat region oligosaccharides but not linkage regions, were reduced with alkaline borohy-dride and fractionated on a Spherisorb column. These oligosaccharides were examined by 600-MHz 1 H NMR spectroscopy using one-and two-dimensional methods and, in addition to some oligosaccharide aldi-tols previously recovered from skeletal keratan sulfate, the following new capping structures were identified: These structures represent seven families of capping residues, whose relative molar proportions are given in parentheses: NeuAc(2-3)-(12%), NeuAc(2-6)-(41%), NeuGc(2-3)-and NeuGc(2-6)-families (12%), Gal(1-3)-(26%), GalNAc(S)(1-3)-(5%), and GlcNAc(S)(1-3)-(4%). It is not clear, at present, where each of these structures occurs on the bi-antennary N-linked corneal keratan sulfate chains, which themselves occur within three keratan sulfate proteoglycan species. However, examination of the relative proportions of the capping to the repeat structures and knowledge of the average molecular size suggests that the sum of these non-reducing termini represents the caps of two antennae. The corneal stroma is mostly an extracellular matrix, which comprises collagens, proteoglycans, and matrix proteins. Its transparency is dependent upon its hydration and the orderly arrangement of the collagen fibrils. The fibrils in mammalian stroma measure 25-30 nm in diameter and have a mean inter-fibrillar distance of 66 nm within lamellae (1). The proteoglycans of the corneal stroma are associated with the collagen fibrils, and they comprise the keratan sulfate (KS) 1 and the chondroitin/dermatan sulfate (CS/DS) families. Electron microscopic studies have shown that four separate proteoglycan binding sites lie within the D period of collagen fibrils in rabbit cornea. The KS proteoglycans were located at the a or c "step" bands and CS/DS proteoglycans were found at the d or e "gap zone." A similar pattern was obtained in bovine cornea (2). On the basis of such studies, Scott has proposed a model (3) for proteoglycan-collagen interactions in cornea in which duplexed glycosaminoglycan chains (both double-stranded DS and KS) may bridge collagen fibrils and thus ensure the precise interfibrillar distances vital for corneal transparency. The major CS/DS proteoglycan of cornea is decorin (4). This is a member of a group of small interstitial proteoglycans, which includes biglycan and fibromodulin that all interact with fibrillar collagens via their protein cores. Recent studies of corneal KS have revealed the existence of several discrete proteoglycans. Originally two core proteins (37 and 25 kDa) were identified (5). Subsequently, two forms of the 37-kDa protein (37A and 37B) were resolved (6). Then, a cDNA clone was isolated and sequenced that coded for a chicken corneal KSPG. This protein, lumican, had a deduced molecular ...
Key indicatorsSingle-crystal X-ray study T = 113 K Mean (C-C) = 0.002 Å R factor = 0.059 wR factor = 0.130 Data-to-parameter ratio = 15.8For details of how these key indicators were automatically derived from the article, see
Key indicatorsSingle-crystal X-ray study T = 113 K Mean (C-C) = 0.003 Å R factor = 0.060 wR factor = 0.158 Data-to-parameter ratio = 17.9For details of how these key indicators were automatically derived from the article, see
Key indicatorsSingle-crystal X-ray study T = 294 K Mean (C-C) = 0.003 Å R factor = 0.036 wR factor = 0.102 Data-to-parameter ratio = 15.7For details of how these key indicators were automatically derived from the article, see
In the paper by Bai, Zhang, Zhang, Zeng & Li [http://scripts.iucr.org/cgi-bin/paper?sj2043], the data relate to the R,R rather than the S,S enantiomer. The revised ellipsoid plot, packing diagram and selected geometrical data are given here.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.