title: Identification in vitreous and molecular cloning of opticin, a novel member of the family of leucine-rich repeat proteins of the extracellular matrix.
abstract: A prominent 45-kDa component was identified by protein staining following SDS-polyacrylamide gel electrophoresis of a 4 M guanidine hydrochloride extract from bovine vitreous collagen fibrils. Peptide sequences obtained from this component were used as a basis for the cloning (from human retinal cDNA) and sequencing of a novel member of the leucine-rich repeat extracellular matrix protein family that we have named opticin. Opticin mRNA was found by reverse transcription polymerase chain reaction in ligament and skin as well as in retina. An open reading frame containing 332 amino acids was identified, the first 19 amino acids representing a signal peptide. The deduced amino acid sequence of the mature protein encodes a 35-kDa protein with a calculated isoelectric point of 5.4. The central domain of this protein consists of six B-type leucine-rich repeats. This domain is flanked by cysteine clusters including a C-terminal two-cysteine cluster containing an additional leucine-rich repeat. The N-terminal region contains a cluster of potential O-glycosylation sites, and analysis of bovine vitreous opticin demonstrated the presence of sialylated O-linked oligosaccharides substituting the core protein. Opticin shows highest protein sequence identity to epiphycan (42%) and osteoglycin (35%) and belongs to Class III of the leucine-rich repeat extracellular matrix protein family.
authors.affiliation: Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, Room 2.14 Stopford Building, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom.
authors.forename: A J
authors.initials: AJ
authors.lastname: Reardon
authors.forename: M
authors.initials: M
authors.lastname: Le Goff
authors.forename: M D
authors.initials: MD
authors.lastname: Briggs
authors.forename: D
authors.initials: D
authors.lastname: McLeod
authors.forename: J K
authors.initials: JK
authors.lastname: Sheehan
authors.forename: D J
authors.initials: DJ
authors.lastname: Thornton
authors.forename: P N
authors.initials: PN
authors.lastname: Bishop
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002417:Cattle; D003094:Collagen / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005109:Extracellular Matrix / Q000737:chemistry*; D016326:Extracellular Matrix Proteins / Q000737:chemistry* / Q000235:genetics* / Q000302:isolation & purification; D006023:Glycoproteins / Q000737:chemistry; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D007930:Leucine / Q000737:chemistry; D008297:Male; D008969:Molecular Sequence Data; D005810:Multigene Family; D010455:Peptides / Q000378:metabolism; D010802:Phylogeny; D011509:Proteoglycans / Q000737:chemistry; D012160:Retina / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D000071232:Small Leucine-Rich Proteoglycans; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014018:Tissue Distribution; D014822:Vitreous Body / Q000737:chemistry*
chemical_list: C119499:EPYC protein, human; D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; C063488:OGN protein, human; C404108:OPTC protein, human; D010455:Peptides; D011509:Proteoglycans; D000071232:Small Leucine-Rich Proteoglycans; D003094:Collagen; D007930:Leucine