Sokawa J, Sokawa Y
J Biochem. 1978 Jun;83(6):1699-705. doi: 10.1093/oxfordjournals.jbchem.a132083.
In 10B601 (rel+) strain possessing a temperature-sensitive valyl-tRNA synthetase, chloramphenicol prevented the formation of guanosine-3'-diphosphate-5'-diphosphate (ppGpp) as well as the stringent control of stable RNA synthesis, under the conditions where the incorporation of valine into protein was still detectable i.e. at the lower restrictive temperatures. On the other hand, the effect of chloramphenicol was not observed at higher restrictive temperatures above 42 degrees C where the incorporation of valine was completely absent. Pretreatment of 10B601 cells with chloramphenicol before transfer to a high restrictive temperature (43.5 degrees C) did retard the onset of accumulation of ppGpp after the shift-up. Duration of the lag period was dependent on the concentration of chloramphenicol added. In parallel with the inability of the cells to accumulate ppGpp, stable RNA synthesis was permitted to continue at that high temperature. These results suggest that chloramphenicol traps aminoacyl-tRNA at the A-sites of ribosomes by damming-up the small flow of aminoacyl-tRNA under the restrictive supply of amino acids. Unchanged tRNA which has been located at the A-site is replaced by the charged one, thus resulting in the suppression of ppGpp formation and in the restoration of stable RNA synthesis.
在具有温度敏感型缬氨酰 - tRNA合成酶的10B601（rel +）菌株中，氯霉素在缬氨酸掺入蛋白质仍可检测到的条件下，即在较低的限制温度下，阻止了鸟苷 - 3'-二磷酸 - 5'-二磷酸（ppGpp）的形成以及稳定RNA合成的严格控制。另一方面，在高于42℃的较高限制温度下未观察到氯霉素的作用，此时缬氨酸的掺入完全不存在。在转移到高限制温度（43.5℃）之前用氯霉素预处理10B601细胞确实会延迟升温后ppGpp积累的开始。延迟期的持续时间取决于添加的氯霉素浓度。与细胞无法积累ppGpp同时，稳定RNA合成在该高温下得以继续。这些结果表明，氯霉素通过在氨基酸供应受限的情况下阻塞少量的氨酰 - tRNA流动，将氨酰 - tRNA捕获在核糖体的A位点。位于A位点的未变化的tRNA被带电荷的tRNA取代，从而导致ppGpp形成的抑制和稳定RNA合成的恢复。
