Fung Angela W S, Payoe Roshani, Fahlman Richard P
Department of Biochemistry, Faculty of Medicine & Dentistry, University of Alberta, 474-MSB Edmonton, AB T6G 2H7, Canada.
Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A1, Canada.
Life (Basel). 2015 Dec 31;6(1):2. doi: 10.3390/life6010002.
Aminoacyl-tRNA protein transferases catalyze the transfer of amino acids from aminoacyl-tRNAs to polypeptide substrates. Different forms of these enzymes are found in the different kingdoms of life and have been identified to be central to a wide variety of cellular processes. L/F-transferase is the sole member of this class of enzyme found in Escherichia coli and catalyzes the transfer of leucine to the N-termini of proteins which result in the targeted degradation of the modified protein. Recent investigations on the tRNA specificity of L/F-transferase have revealed the unique recognition nucleotides for a preferred Leu-tRNA(Leu) isoacceptor substrate. In addition to discussing this tRNA selectivity by L/F-transferase, we present and discuss a hypothesis and its implications regarding the apparent competition for this aminoacyl-tRNA between L/F-transferase and the translational machinery. Our discussion reveals a hypothetical involvement of the bacterial stringent response that occurs upon amino acid limitation as a potential cellular event that may reduce this competition and provide the opportunity for L/F-transferase to readily increase its access to the pool of aminoacylated tRNA substrates.
氨酰-tRNA蛋白质转移酶催化氨基酸从氨酰-tRNA转移至多肽底物。这些酶的不同形式存在于不同的生命王国中，并且已被确定为多种细胞过程的核心。亮氨酸/苯丙氨酸转移酶是在大肠杆菌中发现的这类酶的唯一成员，它催化亮氨酸转移至蛋白质的N端，导致被修饰蛋白质的靶向降解。最近对亮氨酸/苯丙氨酸转移酶的tRNA特异性的研究揭示了一种优选的亮氨酰-tRNA（Leu）同工受体底物的独特识别核苷酸。除了讨论亮氨酸/苯丙氨酸转移酶对这种tRNA的选择性外，我们还提出并讨论了一个假设及其关于亮氨酸/苯丙氨酸转移酶与翻译机制之间对这种氨酰-tRNA明显竞争的影响。我们的讨论揭示了在氨基酸限制时发生的细菌严谨反应作为一种潜在的细胞事件的假设性参与，这可能会减少这种竞争，并为亮氨酸/苯丙氨酸转移酶提供更容易获取氨酰化tRNA底物池的机会。
