Range: ±4 µM
||Bacteria Escherichia coli
||Jewett MC, Miller ML, Chen Y, Swartz JR. Continued protein synthesis at low [ATP] and [GTP] enables cell adaptation during energy limitation.J Bacteriol. 2009 Feb191(3):1083-91PubMed ID19028899
||To measure the dependence of the protein synthesis rate on [ATP] and [GTP], researchers used an in vitro cell-free system derived from E. coli extracts. Cell-free systems provide the opportunity to directly monitor, add, and remove components with much greater ease and accuracy than can be done with in vivo systems.
||Researchers used an integrated Escherichia coli cell-free platform that mimics the intracellular, energy-limited environment to show that protein synthesis rates are governed by simple Michaelis-Menten dependence on [ATP] and [GTP] (K(m)(ATP), 27±4 microM K(m)(GTP), 14±2 microM, BNID 104732). It is interesting that at an ATP concentration of 27 µM, such a synthetase would be expected to function at a rate that is only about 3% of the rate observed with the cytoplasmic ATP concentration present when the organism has an adequate energy source (3 mM). With 27 µM ATP the protein synthesis rate would still be 50% of the prestarvation rate.