Cloning and sequence analysis of rat bone sialoprotein (osteopontin) cDNA reveals an Arg-Gly-Asp cell-binding sequence.
The primary structure of a bone-specific sialoprotein was deduced from cloned cDNA. One of the cDNA clones isolated from a rat osteosarcoma (ROS 17/2.8) phage lambda gt11 library had a 1473-base-pair-long insert that encoded a protein with 317 amino acid residues. This cDNA clone appears to represent the complete coding region of sialoprotein mRNA, including a putative AUG initiation codon and a signal peptide sequence. The amino acid sequence deduced from the cDNA contains several Ser-Xaa-Glu sequences, possibly representing attachment points for O-glycosidically linked oligosaccharides and one Asn-Xaa-Ser sequence representing a likely site for the N-glycosidically linked oligosaccharide. An interesting observation is the Gly-Arg-Gly-Asp-Ser sequence, which is identical to the cell-binding sequence identified in fibronectin. The presence of this sequence prompted us to investigate the cell-binding properties of sialoprotein. The ROS 17/2.8 cells attached and attained a spread morphology on surfaces coated with sialoprotein. We could demonstrate that synthetic Arg-Gly-Asp-containing peptides efficiently inhibited the attachment of cells to sialoprotein-coated substrates. The results show that the Arg-Gly-Asp sequence also confers cell-binding properties on bone-specific sialoprotein. To better reflect the potential function of bone sialoprotein--we propose the name "osteopontin" for this protein.
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001842:Bone and Bones / Q000166:cytology / Q000502:physiology*; D002448:Cell Adhesion; D004247:DNA / Q000235:genetics; D006882:Hydroxyapatites / Q000378:metabolism; D053495:Osteopontin; D051381:Rats; D011956:Receptors, Cell Surface / Q000235:genetics*; D012795:Sialoglycoproteins / Q000235:genetics*
D006882:Hydroxyapatites; D011956:Receptors, Cell Surface; D012795:Sialoglycoproteins; C506897:Spp1 protein, rat; D053495:Osteopontin; D004247:DNA