Mode of action of bolesatine, a cytotoxic glycoprotein from Boletus satanas Lenz. Mechanistic approaches.
Bolesatine is a potent cytotoxic glycoprotein purified from Boletus satanas Lenz, which has previously been shown to be an inhibitor of protein synthesis in several in vitro systems and in vivo. For a better understanding of its mechanism of action on protein synthesis at the ribosomal level, rat liver ribosomes were pretreated with bolesatine (1 to 10 micrograms) added to in vitro polyuridylic acid (poly(U)) translation systems before and after washing. The fact that ribosomes were still active confirmed that bolesatine cannot be included in the group of protein synthesis inhibitors of plant origin, known as ribosome-inactivating proteins (RIPs). The effect of bolesatine on the EF-2 elongation factor and post-ribosomal fraction was then studied in vitro. The results indicated that bolesatine does not have a direct effect on elongation factors, but hydrolyses the nucleoside triphosphates, GTP (80% to 90%, respectively for 1 to 10 micrograms) and ATP (10% to 40%, respectively for 1 to 10 micrograms), with consequent inhibition of protein synthesis. Thus, bolesatine should be classified as a nucleoside triphosphate phosphatase, rather than as a direct inhibitor of protein synthesis. The study of the effect of bolesatine on the EF-2 factor revealed that the mechanism whereby bolesatine affects protein synthesis probably involves GTP hydrolysis rather than EF-2 inhibition.
Ennamany
R
R
Laboratory of Toxicology and Applied Hygiene, University of Bordeaux 2, France.
Lavergne
J P
JP
Reboud
J P
JP
Dirheimer
G
G
Creppy
E E
EE
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001487:Basidiomycota; D005656:Fungal Proteins / Q000008:administration & dosage / Q000302:isolation & purification / Q000493:pharmacokinetics / Q000633:toxicity*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects*; D009183:Mycotoxins / Q000008:administration & dosage / Q000302:isolation & purification / Q000493:pharmacokinetics / Q000633:toxicity*; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000378:metabolism; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors / Q000187:drug effects / Q000378:metabolism; D010649:Phenylalanine / Q000737:chemistry / Q000378:metabolism; D011072:Poly U / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000633:toxicity*; D051381:Rats; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism
D005656:Fungal Proteins; D009183:Mycotoxins; D009419:Nerve Tissue Proteins; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors; D011500:Protein Synthesis Inhibitors; C060924:Bolesatine protein, Boletus satanas; D011072:Poly U; D010649:Phenylalanine; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate