Department of Biochemistry and Biophysics and Center for RNA Biology, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA.
RNA. 2013 Feb;19(2):158-66. doi: 10.1261/rna.035964.112. Epub 2012 Dec 17.
In the absence of elongation factor EF-G, ribosomes undergo spontaneous, thermally driven fluctuation between the pre-translocation (classical) and intermediate (hybrid) states of translocation. These fluctuations do not result in productive mRNA translocation. Extending previous findings that the antibiotic sparsomycin induces translocation, we identify additional peptidyl transferase inhibitors that trigger productive mRNA translocation. We find that antibiotics that bind the peptidyl transferase A site induce mRNA translocation, whereas those that do not occupy the A site fail to induce translocation. Using single-molecule FRET, we show that translocation-inducing antibiotics do not accelerate intersubunit rotation, but act solely by converting the intrinsic, thermally driven dynamics of the ribosome into translocation. Our results support the idea that the ribosome is a Brownian ratchet machine, whose intrinsic dynamics can be rectified into unidirectional translocation by ligand binding.
在缺乏延伸因子 EF-G 的情况下，核糖体在易位的前移位（经典）和中间（杂交）状态之间自发地、热驱动地波动。这些波动不会导致有产物的 mRNA 易位。扩展了先前的发现，即抗生素 sparsomycin 诱导易位，我们确定了其他诱导有产物的 mRNA 易位的肽基转移酶抑制剂。我们发现，结合肽基转移酶 A 位的抗生素诱导 mRNA 易位，而不占据 A 位的抗生素则不能诱导易位。使用单分子 FRET，我们表明，诱导易位的抗生素不会加速亚基间的旋转，而是仅通过将核糖体的固有、热驱动动力学转化为易位来起作用。我们的结果支持这样的观点，即核糖体是一个布朗棘轮机器，其固有动力学可以通过配体结合被纠正为单向易位。
