Abstract：
N-terminal acetylation is widespread in the eukaryotic proteome but in bacteria is restricted to a small number of proteins mainly involved in translation. It was long known that elongation factor Tu (EF-Tu) is N-terminally acetylated, whereas the enzyme responsible for this process was unclear. Here, we report that RimI acetyltransferase, known to modify ribosomal protein S18, is likewise responsible for N-acetylation of the EF-Tu. With the help of inducible tufA expression plasmid, we demonstrated that the acetylation does not alter the stability of EF-Tu. Binding of aminoacyl tRNA to the recombinant EF-Tu in vitro was found to be unaffected by the acetylation. At the same time, with the help of fast kinetics methods, we demonstrate that an acetylated variant of EF-Tu more efficiently accelerates A-site occupation by aminoacyl-tRNA, thus increasing the efficiency of in vitro translation. Finally, we show that a strain devoid of RimI has a reduced growth rate, expanded to an evolutionary timescale, and might potentially promote conservation of the acetylation mechanism of S18 and EF-Tu. This study increased our understanding of the modification of bacterial translation apparatus.
摘要：
N-末端乙酰化在真核蛋白质组中很普遍，但在细菌中仅限于少量主要参与翻译的蛋白质。人们早就知道延伸因子Tu（EF-Tu）是N末端乙酰化的，而负责这一过程的酶尚不清楚。这里,我们报道了RimI乙酰转移酶，已知修饰核糖体蛋白S18，同样负责EF-Tu的N-乙酰化。在诱导型tufA表达质粒的帮助下，我们证明乙酰化不会改变EF-Tu的稳定性。发现氨酰基tRNA在体外与重组EF-Tu的结合不受乙酰化的影响。同时,在快速动力学方法的帮助下，我们证明EF-Tu的乙酰化变体更有效地加速氨酰基-tRNA的A位点占据，从而提高体外翻译的效率。最后,我们表明，缺乏RimI的菌株的生长速率降低，扩展到进化的时间尺度，并可能潜在地促进S18和EF-Tu的乙酰化机制的保留。这项研究增加了我们对细菌翻译装置修饰的理解。
