An aminoacyl-tRNA synthetase complex in Escherichia coli.
Aminoacyl-tRNA synthetases from several strains of Escherichia coli are shown to elute as a high-molecular-weight complex on 6% agarose columns (Bio-Gel A-5M). In contrast, very little synthetase activity was observed in such complexes on Sephadex G-200 columns, suggesting that these enzymes may interact with or are dissociated during chromatography on dextran. The size of the complex observed on Bio-Gel A-5M was influenced by the method of cell breakage and the salt concentrations present in buffers. The largest complexes (greater than 1,000,000 daltons) were seen with cells broken with a freeze press, whereas with sonicated preparations the average size of the complex was about 400,000 daltons. Extraction of synthetases at 0.15 M NaCl, to mimic physiological salt concentrations, also resulted in high-molecular-weight complexes, as demonstrated by both agarose gel filtration and ultracentrifugation analysis. Evidence is presented that dissociation of some synthetases does occur in the presence of higher salt levels (0.4 M NaCl). Partial purification of the synthetase complex on DEAE-Sephacel was accomplished with only minor dissociation of individual synthetases. These data suggest that a complex(es) of aminoacyl-tRNA synthetase does exist in bacterial cells, just as in eucaryotes, and that the complex may have escaped earlier detection due to its fragility during isolation.
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D000604:Amino Acyl-tRNA Synthetases / Q000302:isolation & purification / Q000378:metabolism*; D002458:Cell Fractionation / Q000379:methods; D002850:Chromatography, Gel; D004023:Dictyostelium / Q000201:enzymology; D004926:Escherichia coli / Q000201:enzymology*; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000378:metabolism*
D009097:Multienzyme Complexes; D000604:Amino Acyl-tRNA Synthetases