Mode of Action of Thiolutin, an Inhibitor of Macromolecular Synthesis in Saccharomyces cerevisiae

摘要: Thesulfur-containing antibiotic thiolutin hasbeenshowntobea potent, reversible inhibitor ofthegrowth ofSaccharomyces cerevisiae. Viability was unaffected overtheconcentration rangeof4to100ug/ml. Atconcentrations as lowas2 sg/ml, thedruginhibited ribonucleic acid(RNA)andprotein synthesis inwholecells andspheroplasts. Atthese lowconcentrations, protein continued for ashort period oftimeafter RNAsynthesis completely stopped. Withhigher drugconcentrations (greater than20;g/ml) inhibited; concentrations ofthiolutin up to100,ug/ml didnotaffect translocation orpeptide bondformation incell-free protein-synthesizing systemsfromyeast. Theeffect on theactivity ofpartially purified deoxyribonucleic acid-dependent RNA polymerases examined, andthedrug found tobea potentinhibitor ofRNA invitro. Inhibition greatest whenthe polymerase preincubated withthiolutin. Several mechanisms arediscussed toexplain themultiple effects onS.cerevisiae. Since theaction ofthe drugiseasily reversed, may provetobeofuse instudies ofvarious stages ofyeastgrowth. Inbacteria, antibiotics haveplayed useful roles inproviding genetic markers foranumber ofmacromolecules andhavealso beenusedin dissecting theroles inconcerted reactions. Theuseofantibiotics inyeast hasnotbeenexploited tothesameextent. This isdue,inpart, tothefactthatmanyofthe better-characterized donotaffect Saccharomyces cerevisiae, presumably because theyeastcell isimpermeable tothese compounds. Manyantifungal compounds havebeen isolated during theprocess ofscreening antimicrobial agents, and,although theymay notbemedically oftheir toxicity properties, itisquite possible that someofthese mayhavebiochemical applications. Thisreport describes ourinitial studies onthe modeofaction ofonesuchantifungal agent, thiolutin.