Binding of T-2 toxin to eukaryotic cell ribosomes.
The binding of radiolabeled T-2 to eukaryotic ribosomes was studied. The toxin bound to ribosomes in a time-, temperature- and concentration-dependent manner. The binding was saturable (0.3 nM), reversible at 37 degrees (half-time approximately 2.5 hr) and specific. The stoichiometry was one toxin molecule bound per ribosome. Binding of T-2 appeared to stablize the toxin recognition site to thermal degradation. A synthetically derived epimer of T-2 bound to the same ribosomal site as authentic T-2, but apparently with lower affinity. Two other trichothecene toxins tested blocked the binding of T-2 to ribosomes in a manner reflecting their protein synthesis inhibitory potencies. Anisomycin blocked the binding of T-2 to both isolated ribosomes and cells, whereas emetine blocked binding only to cells. Our data, together with that in the accompanying paper (Middlebrook JL and Leatherman DL, Biochem Pharmacol 38: 3093-3102, 1989), suggest that T-2 interaction with CHO cells is best viewed as a free, bidirectional movement of toxin across the plasma membrane and specific high-affinity binding to ribosomes.
Department of Toxinology, U.S. Army Medical Research Institute of Infectious Diseases, Frederick, MD 21701-5011.
J L
JL
Middlebrook
D L
DL
Leatherman
D000818:Animals; D000841:Anisomycin / Q000378:metabolism; D001667:Binding, Competitive; D002460:Cell Line; D006224:Cricetinae; D007700:Kinetics; D014176:Protein Biosynthesis; D012270:Ribosomes / Q000378:metabolism*; D012717:Sesquiterpenes / Q000378:metabolism*; D013237:Stereoisomerism; D013605:T-2 Toxin / Q000378:metabolism*; D013696:Temperature
D012717:Sesquiterpenes; D000841:Anisomycin; D013605:T-2 Toxin