Semenkov Y u, Shapkina T, Makhno V, Kirillov S
B.P. Konstantinov Petersburg Nuclear Physics Institute, Academy of Sciences, Saint Petersburg district, USSR.
FEBS Lett. 1992 Jan 20;296(2):207-10. doi: 10.1016/0014-5793(92)80380-y.
AcPhe2-tRNA(Phe) synthesized in 70S ribosomes after consecutive binding of AcPhe-tRNA(Phe) at the P sites and EF-Tu-directed binding of Phe-tRNA(Phe) at the A sites is able to react quantitatively with puromycin in the absence of EF-G. A detailed study of the kinetics of the puromycin reaction, its comparison with that of spontaneous translocation, the use of antibiotic viomycin as an effective inhibitor of spontaneous translocation revealed that, besides spontaneous translocation, this peptidyl-tRNA could react with puromycin being located at the A site. This leads to the conclusion that the transpeptidation reaction per se triggers conformational changes in the ribosomal complex bringing the 3'-end of a newly synthesized peptidyl-tRNA nearer to the peptidyl-site of the peptidyltransferase center. This is detected functionally as the ability of such an A site bound peptidyl-tRNA to react with puromycin. This reaction is highly pronounced at elevated (25 degrees C) temperature but can be hardly detected at 0 degrees C.
在70S核糖体中，乙酰苯丙氨酰 - tRNA（Phe）在P位点连续结合乙酰苯丙氨酰 - tRNA（Phe）且苯丙氨酰 - tRNA（Phe）在EF - Tu引导下结合到A位点后合成，在没有EF - G的情况下，它能够与嘌呤霉素定量反应。对嘌呤霉素反应动力学的详细研究、其与自发转位反应动力学的比较以及使用抗生素紫霉素作为自发转位的有效抑制剂表明，除了自发转位外，这种肽基 - tRNA可以与位于A位点的嘌呤霉素反应。这导致得出这样的结论：转肽反应本身会引发核糖体复合物的构象变化，使新合成的肽基 - tRNA的3'端更靠近肽基转移酶中心的肽基位点。从功能上看，这表现为这种结合在A位点的肽基 - tRNA与嘌呤霉素反应的能力。该反应在较高温度（25摄氏度）下非常明显，但在0摄氏度时几乎检测不到。
