Wang M D, Schnitzer M J, Yin H, Landick R, Gelles J, Block S M
Department of Molecular Biology and Princeton Materials Institute, Princeton University, Princeton, NJ 08544, USA.
Science. 1998 Oct 30;282(5390):902-7. doi: 10.1126/science.282.5390.902.
RNA polymerase (RNAP) moves along DNA while carrying out transcription, acting as a molecular motor. Transcriptional velocities for single molecules of Escherichia coli RNAP were measured as progressively larger forces were applied by a feedback-controlled optical trap. The shapes of RNAP force-velocity curves are distinct from those of the motor enzymes myosin or kinesin, and indicate that biochemical steps limiting transcription rates at low loads do not generate movement. Modeling the data suggests that high loads may halt RNAP by promoting a structural change which moves all or part of the enzyme backwards through a comparatively large distance, corresponding to 5 to 10 base pairs. This contrasts with previous models that assumed force acts directly upon a single-base translocation step.
RNA聚合酶（RNAP）在进行转录时沿着DNA移动，充当分子马达。通过反馈控制的光镊施加逐渐增大的力，测量了单个大肠杆菌RNAP分子的转录速度。RNAP力-速度曲线的形状与肌球蛋白或驱动蛋白等运动酶不同，表明在低负荷下限制转录速率的生化步骤不会产生移动。对数据进行建模表明，高负荷可能通过促进一种结构变化来使RNAP停止，这种结构变化会使全部或部分酶向后移动相对较大的距离，相当于5到10个碱基对。这与之前假设力直接作用于单碱基易位步骤的模型形成对比。
