title: Sequence of the precursor to rat bone gamma-carboxyglutamic acid protein that accumulates in warfarin-treated osteosarcoma cells.
abstract: A biosynthetic precursor to rat bone gamma-carboxyglutamic acid protein (BGP) was isolated from warfarin-treated ROS 17/2 osteosarcoma cells by antibody affinity chromatography followed by reverse phase high performance liquid chromatography. Thirty-two residues of its NH2-terminal sequence were determined by gas-phase protein sequence analysis. Comparison of this sequence with the known structure of rat BGP established that the intracellular precursor is a 76-residue molecule of Mr = 9120 that differs from 6000-Da bone BGP in having an NH2-terminal extension of 26 residues. This precursor appears to be generated from the primary translation product by cleavage of a hydrophobic signal peptide and is the probable substrate for gamma-carboxylation by virtue of its accumulation in the presence of warfarin. The putative targeting region for gamma-carboxylation previously identified in the leader sequences of vitamin K-dependent proteins is found in the propeptide portion of the precursor. Since the immunoreactive component secreted by warfarin-treated cells is identical in sequence to the 6000-Da BGP from bone, propeptide cleavage from the precursor is independent of gamma-carboxylation and precedes secretion of BGP from the cell.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001842:Bone and Bones / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000096:biosynthesis*; D002478:Cells, Cultured; D015675:Osteocalcin; D012516:Osteosarcoma / Q000378:metabolism*; D011498:Protein Precursors / Q000032:analysis*; D051381:Rats; D014859:Warfarin / Q000494:pharmacology*
chemical_list: D002135:Calcium-Binding Proteins; D011498:Protein Precursors; D015675:Osteocalcin; D014859:Warfarin