title: Increased isoleucine acceptance by sulfur-deficient transfer RNA from Escherichia coli.
abstract: Sulfur-deficient tRNA, isolated from Escherichia coli HfrC, rel-, met-, cys-, lambda, after cysteine starvation, was found to have an increased acceptance of isoleucine in proportion to the deficiency of 4-thiouridine. Isoleucine acceptance was not altered in the presence of other amino acids of CTP, and the higher acceptance was observed over a wide range of magnesium, isoleucine, tRNA and enzyme concentrations. The Vmax value for sulfur-deficient tRNA was more than three times greater than observed for normal tRNA. Methylated albumin kieselguhr (MAK) chromatography revealed three isoacceptor peak for normal tRNA, while sulfur-deficient tRNA  was missing tRNAile, and exhibited a larger, shifted peaks for tRNA normal tRNA, while sulfur-deficient tRNA was missing tRNAille 2, and exhibited a large shifted peak for tRNAile 3 . Treatment with crude RNA sulfurtransferase both lowered the isoleucine acceptance for sulfur-deficient tRNA to that seen for normal tRNA, and restored the missing isoacceptor on MAK. The possibility that thionucleotides may play a role in the aminoacylation of tRNAile in E. coli is discussed.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D007532:Isoleucine / Q000378:metabolism*; D007700:Kinetics; D009154:Mutation; D012343:RNA, Transfer / Q000302:isolation & purification / Q000378:metabolism*; D013455:Sulfur / Q000172:deficiency*; D013466:Sulfurtransferases / Q000378:metabolism; D046249:Transfer RNA Aminoacylation
chemical_list: D007532:Isoleucine; D013455:Sulfur; D012343:RNA, Transfer; D013466:Sulfurtransferases; D000604:Amino Acyl-tRNA Synthetases