Swedes J S, Sedo R J, Atkinson D E
J Biol Chem. 1975 Sep 10;250(17):6930-8.
When Escherichia coli K-12 strain PC 0294, which is unable to synthesize adenine nucleotides, thereonine, proline, and leucine, was starved for adenine, the concentrations of ATP, ADP, and AMP fell rapidly. The adenylate energy charge was not affected until the adenine nucleotide pool fell to about 30% of its normal value. Similarly, cells in an adenine-limited chemostat grew at intracellular adenine nucleotide pool values as low as 30% of normal, but the energy charge in all cases was approximately 0.90. Incorporation of [14C]leucine into protein in adenine-starved cells continued rapidly as long as the energy charge was in or near its normal range, even when the concentration of ATP was 30% to 10% of its normal value. When glucose was added to cells that had been resuspended in medium lacking both glucose and adenine, the energy charge rose rapidly but the concentration of ATP fell, presumably because of nucleic acid synthesis. The rate of [14C]leucine incorporation into protein rose rapidly while adenine nucleotide concentrations fell, and then declined roughly in parallel with the energy charge. At a given value of energy and of total concentration of adenine nucleotides, the rate of protein synthesis may, of course, vary with the concentrations of precursors and modifiers; thus, the rate cannot be predicted from knowledge only of the energy charge. Our results suggest, however, that the rate of protein synthesis and the capacity for growth are much more sensitive to changes in the value of the energy charge than to changes in the concentration of ATP. Growth occurs when the ATP concentration is reduced to one-third of its normal value, but has not been observed when the energy charge has fallen by as much as 10%.
当无法合成腺嘌呤核苷酸、苏氨酸、脯氨酸和亮氨酸的大肠杆菌K-12菌株PC 0294缺乏腺嘌呤时，ATP、ADP和AMP的浓度迅速下降。在腺嘌呤核苷酸库降至其正常值的约30%之前，腺苷酸能荷不受影响。同样，在腺嘌呤限制的恒化器中的细胞，其细胞内腺嘌呤核苷酸库值低至正常值的30%时仍能生长，但在所有情况下能荷约为0.90。只要能荷处于或接近其正常范围，腺嘌呤饥饿细胞中[14C]亮氨酸掺入蛋白质的过程就会持续快速进行，即使ATP浓度仅为其正常值的30%至10%。当向重悬于缺乏葡萄糖和腺嘌呤的培养基中的细胞添加葡萄糖时，能荷迅速上升，但ATP浓度下降，这可能是由于核酸合成所致。[14C]亮氨酸掺入蛋白质的速率在腺嘌呤核苷酸浓度下降时迅速上升，然后大致与能荷平行下降。当然，在给定的能荷值和腺嘌呤核苷酸总浓度下，蛋白质合成速率可能会因前体和调节剂的浓度而异；因此，仅根据能荷知识无法预测该速率。然而，我们的结果表明，蛋白质合成速率和生长能力对能荷值变化的敏感性远高于对ATP浓度变化的敏感性。当ATP浓度降至其正常值的三分之一时仍会发生生长，但当能荷下降多达10%时则未观察到生长现象。
