title: Isolation and characterization of four type 2 ribosome inactivating pulchellin isoforms from Abrus pulchellus seeds.
abstract: Abrus pulchellus seeds contain at least seven closely related and highly toxic type 2 ribosome-inactivating pulchellins, each consisting of a toxic A-chain linked to a sugar binding B-chain. In the present study, four pulchellin isoforms (termed P I, P II, P III and P IV) were isolated by affinity, ion exchange and chromatofocusing chromatographies, and investigated with respect to toxicity and sugar binding specificity. Half maximal inhibitory concentration and median lethal dose values indicate that P I and P II have similar toxicities and that both are more toxic to cultured HeLa cells and mice than P III and P IV. Interestingly, the secondary structural characteristics and sugar binding properties of the respective pairs of isoforms correlate well with the two toxicity levels, in that P I/P II and P III/P IV form two specific subgroups. From the deduced amino acids sequences of the four isoforms, it is clear that the highest similarity within each subgroup is found to occur within domain 2 of the B-chains, suggesting that the disparity in toxicity levels might be attributed to subtle differences in B-chain-mediated cell surface interactions that precede and determine toxin uptake pathways.
authors.affiliation: Programa de Pós-graduação em Genética e Evolução, Universidade Federal de São Carlos, Brazil.
authors.forename: Priscila V
authors.initials: PV
authors.lastname: Castilho
authors.forename: Leandro S
authors.initials: LS
authors.lastname: Goto
authors.forename: Lynne M
authors.initials: LM
authors.lastname: Roberts
authors.forename: Ana Paula U
authors.initials: AP
authors.lastname: Araújo
mesh_terms: D029912:Abrus / Q000737:chemistry*; D000595:Amino Acid Sequence; D002241:Carbohydrates / Q000737:chemistry; D006367:HeLa Cells; D006384:Hemagglutination / Q000187:drug effects; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D020128:Inhibitory Concentration 50; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity; D017433:Protein Structure, Secondary; D054790:Ribosome Inactivating Proteins, Type 2 / Q000737:chemistry* / Q000302:isolation & purification / Q000633:toxicity*; D012639:Seeds / Q000737:chemistry; D016415:Sequence Alignment
chemical_list: D002241:Carbohydrates; D020033:Protein Isoforms; D054790:Ribosome Inactivating Proteins, Type 2