title: The mechanism of the aminoacylation of transfer ribonucleic acid. The kinetics and stoichiometry of the lysis of aminoacyl-tRNA.
abstract: It is often stated that the aminoacylation of transfer RNA proceeds in discrete steps: (formula: see article). If this is a complete description of the reaction, the reverse overall formation of ATP should not be more rapid than the formation of Enz . (AA approximately AMP). We show for four different amino acid:tRNA ligases that lysis of AA-tRNA (with PPi and AMP) to ATP is faster than lysis of AA-tRNA (with AMP only) to Enz . (AA approximately AMP). This requires that the transition state proceeds from a quaternary complex of PPi, AMP, AA-tRNA and Enz. From the law of microscopic reversibility, this requires that in the forward reaction the AA-tRNA bond be formed before PPi leaves the enzyme complex. Therefore, the forward reaction passes through the quaternary complex Enz . ATP . AA . tRNA. (In view of recent evidence of the specific requirement of two cations, the complex is accurately described as senary).
mesh_terms: D000249:Adenosine Monophosphate / Q000378:metabolism; D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D011756:Diphosphates / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D006868:Hydrolysis; D007700:Kinetics; D012343:RNA, Transfer / Q000378:metabolism; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*
chemical_list: D011756:Diphosphates; D012346:RNA, Transfer, Amino Acyl; D000249:Adenosine Monophosphate; D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases