title: Proteoglycans contain a 4.6 A repeat in muscular dystrophy corneas: x-ray diffraction evidence.
abstract: Synchrotron x-ray diffraction patterns from macular corneal dystrophy (MCD) corneas contain an unusual reflection that arises because of an undefined ultrastructure with a periodic repeat in the region of 4.6 A. In this study, we compared with wide-angle x-ray diffraction patterns obtained from four normal human corneas and four MCD corneas. Moreover, portions of two of the MCD corneas were pretreated with a specific glycosidase to shed light on the origin of the 4.6 A reflection. None of the normal corneas produced an x-ray reflection in the region of 4.6 A, whereas all four of the MCD corneas did (MCD type I at 4.65 A and 4.63 A, MCD type II at 4.63 A and 4.67 A). This reflection was diminished after incubation of the MCD tissues with either chondroitinase ABC or N-glycanase. The findings indicate that glycosaminoglycans or proteoglycans contribute to the unusual MCD x-ray reflection and hence most likely contain a periodic 4.6 A ultrastructure. Furthermore, the results imply that periodic 4.6 A MCD ultrastructures reside in either intact, unsulfated lumican molecules and regions of the CS/DS-containing molecules or in a region of a hybrid macromolecular aggregate formed by the interaction of the two molecules.
authors.affiliation: Anheuser-Busch Eye Institute, Department of Ophthalmology, St. Louis University School of Medicine, Missouri 63104, USA. quantoaj@sluvca.slu.edu
authors.forename: A J
authors.initials: AJ
authors.lastname: Quantock
authors.forename: G K
authors.initials: GK
authors.lastname: Klintworth
authors.forename: D J
authors.initials: DJ
authors.lastname: Schanzlin
authors.forename: M S
authors.initials: MS
authors.lastname: Capel
authors.forename: M E
authors.initials: ME
authors.lastname: Lenz
authors.forename: E J
authors.initials: EJ
authors.lastname: Thonar
mesh_terms: D000328:Adult; D000368:Aged; D000581:Amidohydrolases / Q000494:pharmacology; D055592:Biophysical Phenomena; D001703:Biophysics; D002808:Chondroitin Lyases / Q000494:pharmacology; D003094:Collagen / Q000032:analysis; D003315:Cornea / Q000737:chemistry* / Q000187:drug effects; D003317:Corneal Dystrophies, Hereditary / Q000378:metabolism*; D005260:Female; D006025:Glycosaminoglycans / Q000032:analysis; D006801:Humans; D007632:Keratan Sulfate / Q000032:analysis; D046911:Macromolecular Substances; D008297:Male; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D011509:Proteoglycans / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D006025:Glycosaminoglycans; D046911:Macromolecular Substances; D011509:Proteoglycans; D003094:Collagen; D007632:Keratan Sulfate; D000581:Amidohydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D002808:Chondroitin Lyases