Protection of rat liver 80 S ribosomes against ricin A chain inactivation by proteins extracted from rat liver and wheat germ ribosomal subunits with ammonium chloride/magnesium chloride.
Proteins extracted from wheat germ 60 S ribosomal subunits and rat liver 60 S and 40 S ribosomal subunits with 3 M NH4Cl/75 mM MgCl2 were able to prevent the ricin A chain-mediated inactivation of untreated 80 S rat liver ribosomes. The protection of polyphenylalanine synthetic capability of 80 S ribosomes was saturable and reached 100% protection in the presence of about 20 micrograms of extracted protein using a uniform set of assay conditions. No protection was observed using proteins extracted from wheat germ 40 S subunits or the core fraction of rat liver 60 S subunits or protein extracted from Escherichia coli ribosomes or ribosomal subunits. The conclusion that the protective effect of extracted 60 S subunit proteins was specific, was further strengthened by showing that unrelated proteins such as alpha-lactalbumin, bovine serum albumin and lysozyme, and polypeptides such as polylysine and poly(aspartic acid), also showed no protection. If 80 S ribosomes were first treated with ricin A chain and then incubated with proteins extracted from rat liver 60 S subunits, no protection was observed. Proteins extracted with NH4Cl/MgCl2 from 60 S rat liver subunits were applied to carboxymethylcellulose column equilibrated with 6 M urea. Stepwise elution with increasing concentrations of LiCl resulted in seven fractions. One fraction (D) contained most of the protective factor; one fraction (E) contained a lesser amount of the protective factor. Two-dimensional polyacrylamide gel electrophoresis of fraction D showed the presence of ten proteins. These data are consistent with the idea that the enzymatic target of ricin A chain is protein is nature and that fraction D contains one or more proteins that appear to act as a inhibitor against ricin A chain.
D000643:Ammonium Chloride / Q000494:pharmacology*; D000818:Animals; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology*; D015636:Magnesium Chloride; D037121:Plant Lectins; D010944:Plants / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D051381:Rats; D012269:Ribosomal Proteins / Q000502:physiology*; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D012276:Ricin / Q000494:pharmacology*; D014908:Triticum / Q000378:metabolism
D037121:Plant Lectins; D012269:Ribosomal Proteins; D000643:Ammonium Chloride; D015636:Magnesium Chloride; D012276:Ricin; D008274:Magnesium