title: Cell-free synthesis of rat preproinsulins: characterization and partial amino acid sequence determination.
abstract: Whole nucleic acid fractions of isolated rat islets of Langerhans greatly stimulate incorporation of radioactive amino acids into protein in a wheat germ ribosomal system. Approximately 30% of the synthetic product is precipitated with antisera to insulin or proinsulin. Characterization of this material by gel chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates a molecular mass of 11,500 daltons. Trypsin digestion releases intact A chain as well as tryptic fragments of the C-peptides and B chains of the two rat proinsulins. Automated sequence determination of labeled cell-free product purified by immunoprecipitation discloses the presence of 23 additional amino acids NH2-terminal to the B chain sequence of proinsulin. The partial amino acid sequence of this extension is as follows: NH2-X-Leu (Lys) Met-x-Phe-Leu-Phe-Leu-Leu (Lys) Leu-Leu-x-leu-X-X-X-X-X-X-X-X-proinsulin. On the basis of the above evidence we have designated this peptide preproinsulin.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D007515:Islets of Langerhans / Q000648:ultrastructure; D008970:Molecular Weight; D011384:Proinsulin / Q000032:analysis / Q000096:biosynthesis*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats
chemical_list: D012333:RNA, Messenger; D011384:Proinsulin