Details

Autor(en) / Beteiligte

• Parker, Jack
• Flashner, Michael
• McKeever, W. Galen
• Neidhardt, Frederick C.

Titel

Metabolic Regulation of the Arginyl and Valyl Transfer Ribonucleic Acid Synthetases in Bacteria

Ist Teil von

• The Journal of biological chemistry, 1974-02, Vol.249 (4), p.1044-1053

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

1974

Quelle

MEDLINE

Beschreibungen/Notizen

• The arginyl and valyl transfer ribonucleic acid synthetases (EC 6.1.13 and EC 6.1.1.9, respectively) in various strains of Escherichia coli and Salmonella typhimurium were measured over a wide range of steady state growth rates. Both enzymes were found to increase approximately 2.5-fold in specific activity over a 7-fold increase in growth rate. Appropriate tests indicated that this change was not the result of stimulation or inhibition of enzyme activity. Use of antibodies prepared against purified valyl-tRNA synthetase revealed differences in the amount of this enzyme in cell-free extracts of cultures grown at different growth rates. By use of a sequential labeling technique it was possible to demonstrate that the low activity of these two enzymes in extracts from slow growing cultures was not caused by specific degradation. During transitions in growth rates brought about by shifts in media, the activity of each of these enzymes changed similarly to the accumulation of RNA, and not in a manner one would predict for enzymes regulated by amino acid supply. By sequential labeling it was shown that the increased differential rate of activity accumulation seen for these enzymes after a shift up was the result of an increased differential rate of synthesis. The pattern of regulation of the arginyl- and valyl-tRNA synthetases seen in steady state cultures and during growth rate transitions has been termed metabolic regulation. The regulation of these two enzymes is similar under these conditions to that of other members of the bacterial cell's protein synthesizing machinery, and is difficult to reconcile with an amino acid mediated repression of these enzymes.