title: Purification of a new ribosome-inactivating protein from the seeds of Cinnamomum porrectum and characterization of the RNA N-glycosidase activity of the toxic protein.
abstract: Porrectin, a new type II ribosome-inactivating protein (RIP), was purified from the seeds of the camphor tree (Cinnamomum porrectum) by affinity chromatography on acid-treated Sepharose 4B. Porrectin is a glycoprotein (M(r)64,500, sugar content 2.5%) consisting of an A-chain (M(r)30,500) and a B-chain (M(r)33,500) linked by the disulfide bond. The terminal sugar of glycan in porrectin B-chain is determined to be mannose. By non-denaturing polyacrylamide gel electrophoresis, porrectin displayed three isoforms that have different pl values with the same molecular weight. Porrectin is a potent inhibitor of eukaryotic protein synthesis in the rabbit reticulocyte lysate system. The molecular mechanism of action of porrectin on rat liver ribosomes is demonstrated to be specific for RNA N-glycosidase. The cleavage site is the adenosine at position 4324 (rat liver 28S rRNA) embedded in the highly conserved ricin/alpha-sarcin ('R/S') domain.
authors.affiliation: Shanghai Institute of Biochemistry, Academia Sinica, China.
authors.forename: X D
authors.initials: XD
authors.lastname: Li
authors.forename: W Y
authors.initials: WY
authors.lastname: Liu
authors.forename: C L
authors.initials: CL
authors.lastname: Niu
mesh_terms: D020418:Algal Proteins; D000818:Animals; D002241:Carbohydrates / Q000737:chemistry; D006384:Hemagglutination / Q000187:drug effects; D008099:Liver / Q000187:drug effects; D008970:Molecular Weight; D009699:N-Glycosyl Hydrolases / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D011506:Proteins; D011817:Rabbits; D051381:Rats; D054788:Ribosome Inactivating Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D012270:Ribosomes / Q000187:drug effects*; D012639:Seeds / Q000737:chemistry*; D014197:Trees
chemical_list: D020418:Algal Proteins; D002241:Carbohydrates; D010940:Plant Proteins; D011500:Protein Synthesis Inhibitors; D011506:Proteins; D054790:Ribosome Inactivating Proteins, Type 2; C104406:camphorin protein, Cinnamomum camphora; C061930:cinnamomin, Phytophthora cinnamomi; D009699:N-Glycosyl Hydrolases; D054788:Ribosome Inactivating Proteins