title: Similarity between the major collagens of cuttlefish cranial cartilage and cornea.
abstract: Invertebrates possess unique collagen-containing connective tissue elements, the biochemistry of which is not clearly understood. We previously reported the occurrence of a novel heterotrimeric type V/XI like collagen in the cranial cartilage of the cuttlefish Sepia officinalis. We report here the purification of the three chains by ion exchange chromatography and the physicochemical characteristics of this collagen. This collagen shared substantial similarity to the collagen purified from the cornea of S. officinalis, with respect to chain composition, cyanogen bromide peptide profile and amino acid composition. The mobility of the C3 chain was retarded in the corneal collagen, which also had an increased glycine content and a smaller ratio of hydroxylysine to lysine, together with a reduction in bound carbohydrates. The cartilage collagen had a higher denaturation temperature than corneal collagen. As observed by transmission electron microscopy of reconstituted fibrils, the heterotrimeric invertebrate collagen formed fibrils of no apparent periodicities as opposed to the regular 64-nm banding pattern of milk shark (Rhizoprionodon acutus) cartilage collagen. This is also the first report on the molecular species of collagen in an invertebrate cornea. Our results strongly support the functioning of minor vertebrate collagens as major collagens in some invertebrates, close similarity of collagens in two tissues with different functions and would hold significance to our understanding of collagen polymorphism and the evolution of the extracellular matrix.
authors.affiliation: Department of Biochemistry, Central Leather Research Institute, Adyar, Chennai 600 020, India. sivakumarp@umkc.edu
authors.forename: Pitchumani
authors.initials: P
authors.lastname: Sivakumar
authors.forename: Lonchin
authors.initials: L
authors.lastname: Suguna
authors.forename: Gowri
authors.initials: G
authors.lastname: Chandrakasan
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D005075:Biological Evolution; D002356:Cartilage / Q000737:chemistry* / Q000378:metabolism*; D002852:Chromatography, Ion Exchange; D003094:Collagen / Q000737:chemistry* / Q000378:metabolism; D003315:Cornea / Q000378:metabolism* / Q000648:ultrastructure; D003488:Cyanogen Bromide / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D008854:Microscopy, Electron; D008974:Mollusca / Q000378:metabolism*; D011489:Protein Denaturation; D012886:Skull / Q000378:metabolism* / Q000648:ultrastructure; D013696:Temperature
chemical_list: D000596:Amino Acids; D003094:Collagen; D003488:Cyanogen Bromide