title: Probing the domain structure of abrin-a by tryptic digestion.
abstract: Abrin-a is a potent plant toxin that consists of A and B chains linked by a disulfide bond. The abrin-a A chain (AaTA) has N-glycosidase activity while the abrin-a B chain (AaTB) has galactose-binding activity. By partial tryptic digestion, the domain structure of abrin-a was investigated. Seven tryptic fragments with molecular masses greater than 3500 Da were isolated and characterized. One fragment, designated T-21 and consisting of 153 amino acid residues, contained the major part of the second domain of AaTB and, after cross-linking of T-21 with glutaraldehyde, the reaction product had the same level of hemagglutinating activity as native abrin. When the T-21 fragment was conjugated with AaTA, the conjugate inhibited protein biosynthesis in HeLa cells. This suggests that the T-21 fragment is able to bind specifically to cells; its conjugate facilitates membrane translocation of AaTA into cells and consequently inhibits protein biosynthesis. T-21, with a molecular mass less than AaTB, is therefore a potentially useful substance for the preparation of immunotoxins.
authors.affiliation: Institute of Biochemistry, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China.
authors.forename: S H
authors.initials: SH
authors.lastname: Lin
authors.forename: L P
authors.initials: LP
authors.lastname: Chow
authors.forename: Y L
authors.initials: YL
authors.lastname: Chen
authors.forename: Y C
authors.initials: YC
authors.lastname: Liaw
authors.forename: J K
authors.initials: JK
authors.lastname: Chen
authors.forename: J Y
authors.initials: JY
authors.lastname: Lin
mesh_terms: D000036:Abrin / Q000737:chemistry* / Q000235:genetics / Q000633:toxicity; D000595:Amino Acid Sequence; D000818:Animals; D003432:Cross-Linking Reagents; D006367:HeLa Cells; D066298:In Vitro Techniques; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000633:toxicity; D014176:Protein Biosynthesis; D011487:Protein Conformation; D011817:Rabbits; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism; D014357:Trypsin
chemical_list: D003432:Cross-Linking Reagents; D010446:Peptide Fragments; D000036:Abrin; D014357:Trypsin