Osteoadherin, a cell-binding keratan sulfate proteoglycan in bone, belongs to the family of leucine-rich repeat proteins of the extracellular matrix.
Osteoadherin is a recently described bone proteoglycan containing keratan sulfate. It promotes integrin (alphav beta3)-mediated cell binding (Wendel, M., Sommarin, Y., and Heinegârd, D. (1998) J. Cell Biol. 141, 839-847). The primary structure of bovine osteoadherin has now been determined by nucleotide sequencing of a cDNA clone from a primary bovine osteoblast expression library. The entire translated primary sequence corresponds to a 49,116-Da protein with a calculated isoelectric point for the mature protein of 5.2. The dominating feature is a central region consisting of 11 B-type, leucine-rich repeats ranging in length from 20 to 30 residues. The full, primary sequence contains four putative sites for tyrosine sulfation, three of which are at the N-terminal end of the molecule. There are six potential sites for N-linked glycosylation present. Osteoadherin shows highest sequence identity, 42%, to bovine keratocan and 37-38% identity to bovine fibromodulin, lumican, and human PRELP. Unique to osteoadherin is the presence of a large and very acidic C-terminal domain. The distribution of cysteine residues resembles that of other leucine-rich repeat proteins except for two centrally located cysteines. Northern blot analysis of RNA samples from various bovine tissues showed a 4.5-kilobase pair message for osteoadherin to be expressed in bone only. Osteoadherin mRNA was detected by in situ hybridization in mature osteoblasts located superficially on trabecular bone.
Sommarin
Y
Y
Department of Cellular and Molecular Biology, Section for Connective Tissue Biology, Lund University, S-221 00 Lund, Sweden. yngve.sommarin@medkem.lu.se
Wendel
M
M
Shen
Z
Z
Hellman
U
U
Heinegârd
D
D
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D001842:Bone and Bones / Q000378:metabolism*; D002417:Cattle; D011508:Chondroitin Sulfate Proteoglycans / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D017403:In Situ Hybridization; D007632:Keratan Sulfate / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D007930:Leucine / Q000032:analysis*; D000071234:Lumican; D008969:Molecular Sequence Data; D011485:Protein Binding; D011509:Proteoglycans / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D011508:Chondroitin Sulfate Proteoglycans; D018076:DNA, Complementary; D016326:Extracellular Matrix Proteins; C000604306:LUM protein, human; D000071234:Lumican; D011509:Proteoglycans; D012333:RNA, Messenger; C113360:osteoadherin; D007632:Keratan Sulfate; D007930:Leucine