Wolf H, Chinali G, Parmeggiani A
Proc Natl Acad Sci U S A. 1974 Dec;71(12):4910-4. doi: 10.1073/pnas.71.12.4910.
Kirromycin, a new inhibitor of protein synthesis, is shown to interfere with the peptide transfer reaction by acting on elongation factor Tu (EF-Tu). All the reactions associated with this elongation factor are affected. Formation of the EF-Tu.GTP complex is strongly stimulated. Peptide bond formation is prevented only when Phe-tRNA(Phe) is bound enzymatically to ribosomes, presumably because GTP hydrolysis associated with enzymatic binding of Phe-tRNA(Phe) is not followed by release of EF-Tu.GDP from the ribosome. This antibiotic also enables EF-Tu to catalyze the binding of Phe-tRNA(Phe) to the poly(U).ribosome complex even in the absence of GTP. EF-Tu activity in the GTPase reaction is dramatically affected by kirromycin: GTP hydrolysis, which normally requires ribosomes and aminoacyl-tRNA, takes place with the elongation factor alone. This GTPase shows the same K(m) for GTP as the one dependent on Phe-tRNA(Phe) and ribosomes in the absence of the antibiotic. Ribosomes and Phe-tRNA(Phe), but not tRNA(Phe) or Ac-Phe-tRNA(Phe), stimulate the kirromycin-induced EF-Tu GTPase. These results indicate that the catalytic center of EF-Tu GTPase that is dependent upon aminoacyl-tRNA and ribosomes is primarily located on the elongation factor. In conclusion, kirromycin can substitute for GTP, aminoacyl-tRNA, or ribosomes in various reactions involving EF-Tu, apparently by affecting the allosteric controls between the sites on the EF-Tu molecule interacting with these components.
奇霉素是一种新型蛋白质合成抑制剂，已证明它通过作用于延伸因子Tu（EF-Tu）来干扰肽转移反应。与该延伸因子相关的所有反应均受到影响。EF-Tu·GTP复合物的形成受到强烈刺激。仅当苯丙氨酰-tRNA（Phe）通过酶促作用与核糖体结合时，肽键形成才会被阻止，推测这是因为与苯丙氨酰-tRNA（Phe）的酶促结合相关的GTP水解之后，EF-Tu·GDP并未从核糖体上释放。这种抗生素甚至在没有GTP的情况下也能使EF-Tu催化苯丙氨酰-tRNA（Phe）与聚（U）·核糖体复合物的结合。奇霉素对GTPase反应中的EF-Tu活性有显著影响：通常需要核糖体和氨酰-tRNA的GTP水解，在仅存在延伸因子时就会发生。这种GTPase对GTP的K（m）值与在没有抗生素时依赖于苯丙氨酰-tRNA（Phe）和核糖体的GTPase相同。核糖体和苯丙氨酰-tRNA（Phe），而非tRNA（Phe）或乙酰苯丙氨酰-tRNA（Phe），会刺激奇霉素诱导的EF-Tu GTPase。这些结果表明，依赖于氨酰-tRNA和核糖体的EF-Tu GTPase的催化中心主要位于延伸因子上。总之，奇霉素在涉及EF-Tu的各种反应中可以替代GTP、氨酰-tRNA或核糖体，显然是通过影响EF-Tu分子上与这些成分相互作用的位点之间的变构调控来实现的。
