title: Aminoacyl transfer RNA formation. VII. Lack of correlation between aminoacylation and PPi-ATP exchange catalyzed by isoleucyl-tRNA synthetase of Escherichia coli in the presence of various divalent cations.
abstract: Isoleucyl-tRNA formation and isoleucine-dependent PPi-ATP exchange catalyzed by purified isoleucyl-tRNA synthetase [EC 6.1.1.5] of Escherichia coli were studied in the presence of various amounts of either Mg2+, Ca2+, Fe2+, Ni2+, or Cu2+. In the presence of Mg2+, isoleucine-dependent PPi-ATP exchange was observed in parallel with isoleucyl-tRNA formation, while in the presence of Ca2+, isoleucyl-tRNA formation was observed without isoleucine-dependent PPi-ATP exchange. Moreover, isoleucine-dependent PPi-ATP exchange was much more in the presence of Fe2+ than in the presence of Mg2+, while little isoleucyl-tRNA was formed in the presence of Fe2+. In the presence of Ni2+ or Cu2+, neither reaction was observed. These data, indicating that formation of an isoleucyl-AMP-enzyme complex is not a necessary step in isoleucyl-tRNA formation, support the existence of a concerted mechanism of isoleucyl-tRNA formation in E. coli.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology*; D003300:Copper / Q000494:pharmacology; D011756:Diphosphates / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D005296:Ferrous Compounds / Q000494:pharmacology; D007532:Isoleucine; D007533:Isoleucine-tRNA Ligase / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D009532:Nickel / Q000494:pharmacology; D012343:RNA, Transfer / Q000378:metabolism*; D046249:Transfer RNA Aminoacylation
chemical_list: D002413:Cations, Divalent; D011756:Diphosphates; D005296:Ferrous Compounds; D007532:Isoleucine; D003300:Copper; D009532:Nickel; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases; D007533:Isoleucine-tRNA Ligase; D008274:Magnesium; D002118:Calcium