title: Studies on human alpha-fetoprotein. Isolation and characterization of monomeric and polymeric forms and amino-terminal sequence analysis.
abstract: Human alpha-fetoprotein has been isolated from the serum and ascitic fluid of a patient with hepatoma by a combination of immunoadsorbent column chromatography and Sephadex G-150 gel filtration. Human alpha-fetoprotein is a sialylated glycoprotein with an estimated molecular weight of 67 500, composed of a single-chain polypeptide of approximately 580 amino acid residues and 3.6% carbohydrate. It is a negatively charged protein with an acid isoelectric point (pH 4.57). In addition to the monomeric form of alpha-fetoprotein, we have identified human alpha-fetoprotein polymers, including dimeric and trimeric forms, which dissociate to the monomer only upon exposure to disulfide-reducing reagents, implying that their formation is dependent upon intermolecular disulfide bonds. These polymers are found in human alpha-fetoprotein isolated by isoelectric focusing in both the major (pI 4.57) and minor (pI 5.2) alpha-fetoprotein fractions. The first 17 residues of the NH2-terminal amino acid sequence of the hepatoma-derived human alpha-fetoprotein have been identified. Fetal alpha-fetoprotein is indistinguishable from hepatoma alpha-fetoprotein by several criteria, including immunoelectrophoresis, acryalmide gel electrophoresis, and proclivity for dimerization.
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D002241:Carbohydrates / Q000032:analysis; D006528:Carcinoma, Hepatocellular / Q000097:blood; D005260:Female; D005333:Fetus; D006801:Humans; D007122:Immunoelectrophoresis; D008113:Liver Neoplasms / Q000097:blood; D046911:Macromolecular Substances; D011247:Pregnancy; D012794:Sialic Acids / Q000032:analysis; D000509:alpha-Fetoproteins / Q000302:isolation & purification
chemical_list: D000596:Amino Acids; D002241:Carbohydrates; D046911:Macromolecular Substances; D012794:Sialic Acids; D000509:alpha-Fetoproteins