Purification and properties of methionyl-transfer-ribonucleic acid synthetase from Escherichia coli.
1. Methionyl-t-RNA synthetase (where t-RNA denotes ;soluble' or transfer RNA) has been purified to apparent homogeneity from a ribonuclease I-free strain of Escherichia coli. Polyacrylamide-gel electrophoresis of the final product revealed a single band. The purified enzyme catalyses the exchange of 450mumoles of pyrophosphate into ATP/mg. in 15min. at 37 degrees . 2. Methionyl-t-RNA synthetase is specific for the l-isomer of methionine, but appears to catalyse the methionylation of two distinct species of t-RNA, both of which are specific for methionine, but only one of which may be subsequently formylated. 3. The Michaelis constant for l-methionine is 2x10(-4)m in the ATP-PP(i) exchange assay and 2x10(-5)m for the acylation of t-RNA. 4. Gel filtration of both crude and highly purified preparations of methionyl-t-RNA synthetase on Sephadex G-200 indicates that the active species of enzyme has a molecular weight of about 190000. The amino acid composition of the enzyme is similar to those reported for the isoleucine and tyrosine enzymes from E. coli.
D000255:Adenosine Triphosphate; D000596:Amino Acids / Q000032:analysis; D001322:Autoanalysis; D002384:Catalysis; D002845:Chromatography; D002850:Chromatography, Gel; D011756:Diphosphates; D004589:Electrophoresis, Disc; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008025:Ligases / Q000032:analysis*; D008715:Methionine; D008970:Molecular Weight; D012343:RNA, Transfer
D000596:Amino Acids; D011756:Diphosphates; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D008715:Methionine; D008025:Ligases