硫链丝菌素对大肠杆菌起始因子2循环利用的影响。
Effect of thiostrepton on recycling of Escherichia coli initiation factor 2.
作者信息
Mazumder R
出版信息
Proc Natl Acad Sci U S A. 1973 Jul;70(7):1939-42. doi: 10.1073/pnas.70.7.1939.
The recycling of initiation factor 2, which requires both GTP and the 50S subunit and involves GTP hydrolysis, appears to be blocked by thiostrepton. However, this antibiotic has little or no effect on the AUG-directed ribosomal binding promoted by initiation factor 2 of fMet-tRNA under conditions that do not permit optimal recycling of the factor. Evidence is presented suggesting that the 50S ribosomal proteins L7 or L12, which are required for the function of the chain elongation factors Tu and G and the accompanying hydrolysis of GTP, are also involved in recycling of initiation factor 2. Although both 5'-guanylylmethylene diphosphonate and thiostrepton seem to block recycling of initiation factor 2, fMet-tRNA bound to the ribosomes in the presence of GTP and thiostrepton can react with puromycin, whereas that bound in the presence of 5'-guanylylmethylene diphosphonate and the antibiotic cannot. It is proposed that initiation factor 2 may interact with two nonidentical ribosomal sites during polypeptide chain initiation.
起始因子2的循环利用需要GTP和50S亚基，并涉及GTP水解，硫链丝菌素似乎会阻断这一过程。然而，在不允许该因子进行最佳循环利用的条件下，这种抗生素对甲酰甲硫氨酸 - tRNA的起始因子2所促进的AUG指导的核糖体结合几乎没有影响。有证据表明，链延长因子Tu和G的功能以及伴随的GTP水解所必需的50S核糖体蛋白L7或L12也参与起始因子2的循环利用。虽然5'-鸟苷基亚甲基二膦酸酯和硫链丝菌素似乎都能阻断起始因子2的循环利用，但在GTP和硫链丝菌素存在的情况下与核糖体结合的甲酰甲硫氨酸 - tRNA能与嘌呤霉素反应，而在5'-鸟苷基亚甲基二膦酸酯和抗生素存在的情况下结合的甲酰甲硫氨酸 - tRNA则不能。有人提出，在多肽链起始过程中，起始因子2可能与两个不同的核糖体位点相互作用。
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