title: The role of structural domains in RIP II toxin model membrane binding.
abstract: The interaction of plant toxin ricin and MLI binding subunits to liposomes containing monosialoganglioside (GM1), bearing a terminal galactose residue, has been examined as a possible receptor model. For the first time we demonstrate that ricin B-chain but not ricin provokes liposome aggregation at 10 M% GM1 concentration, whereas in the presence of either ricin A-chain or galactose the aggregation is inhibited. The B-subunit of plant toxin MLI from Viscum album has similar lectin specificity and activity but cannot aggregate GM1 liposomes. The ability of the B-chain to aggregate liposomes adds a new crucial step in the toxin transmembrane penetration mechanism. We demonstrate here possible ricin B-chain interactions with membranes proceeding via two sites, namely (a) a galactose-binding domain and (b) a hydrophobic interchain domain. In close contact with two phospholipid bilayers, ricin B-chain may determine the geometry of the fusion site. These events can provoke A-chain translocation which follows membrane fusion.
authors.affiliation: State Scientific Center for Genetics and Selection of Microorganisms, GosNIIGENETIKA, Moscow, Russian Federation.
authors.forename: I I
authors.initials: II
authors.lastname: Agapov
authors.forename: A G
authors.initials: AG
authors.lastname: Tonevitsky
authors.forename: A T
authors.initials: AT
authors.lastname: Shamshiev
authors.forename: E
authors.initials: E
authors.lastname: Pohl
authors.forename: P
authors.initials: P
authors.lastname: Pohl
authors.forename: R A
authors.initials: RA
authors.lastname: Palmer
authors.forename: M P
authors.initials: MP
authors.lastname: Kirpichnikov
mesh_terms: D001665:Binding Sites; D002470:Cell Survival / Q000187:drug effects; D004134:Dimyristoylphosphatidylcholine; D005677:G(M1) Ganglioside; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019169:Jurkat Cells; D008051:Lipid Bilayers; D008081:Liposomes / Q000378:metabolism*; D028321:Plant Preparations; D010940:Plant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D012276:Ricin / Q000737:chemistry / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014118:Toxins, Biological / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008051:Lipid Bilayers; D008081:Liposomes; D028321:Plant Preparations; D010940:Plant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D014118:Toxins, Biological; C009674:ribosome inactivating protein, Viscum; D005677:G(M1) Ganglioside; D012276:Ricin; D004134:Dimyristoylphosphatidylcholine