title: A 70000-molecular-weight protein isolated from purified pig gastric mucus glycoprotein by reduction of disulphide bridges and its implication in the polymeric structure.
abstract: The glycoprotein of pig gastric mucus has been isolated free of non-covalently bound protein as judged by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and equilibrium density-gradient centrifugation. After reduction with 0.2 M-mercaptoethanol, protein was released from the glycoprotein, which consisted of a major 70000-mol.wt. component and a minor 60000-mol.wt. component. The 70000-mol.wt. protein fraction was separated from the reduced glycoprotein by either density-gradient centrifugation in CsCl or by gel filtration. Analysis of the 70000-mol.wt. protein fraction showed that, within the limits of the analysis, it was non-glycosylated, and its amino acid analysis was quite different from that of the reduced glycoprotein, which is high in serine, threonine and proline. There was a ratio of one 70000-mol.wt. protein per native glycoprotein molecule of 2 X 10(6) mol.wt. Dissociation of the native glycoprotein into glycoprotein subunits (5 X 10(5) mol.wt.) by reduction or proteolysis results in the release or hydrolysis respectively of the 70000-mol.wt. protein. A similar 70000-mol.wt. protein is demonstrated in human gastric mucus glycoprotein. A structural role for the proteins in these mucus glycoproteins is proposed.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001704:Biopolymers; D003378:Counterimmunoelectrophoresis; D004220:Disulfides / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005753:Gastric Mucosa / Q000032:analysis*; D006023:Glycoproteins / Q000378:metabolism*; D008970:Molecular Weight; D010084:Oxidation-Reduction; D011506:Proteins / Q000302:isolation & purification* / Q000378:metabolism; D013552:Swine
chemical_list: D000596:Amino Acids; D001704:Biopolymers; D004220:Disulfides; D006023:Glycoproteins; D011506:Proteins