Department of Physics, Universita degli Studi di Cagliari and Sardinian Laboratory for Computational Materials Science, Monserrato, Italy.
Biophys J. 2010 Feb 17;98(4):569-75. doi: 10.1016/j.bpj.2009.10.045.
Our aim in this study was to provide an atomic description of ampicillin translocation through OmpF, the major outer membrane channel in Escherichia coli and main entry point for beta-lactam antibiotics. By applying metadynamics simulations, we also obtained the energy barriers along the diffusion pathway. We then studied the effect of mutations that affect the charge and size at the channel constriction zone, and found that in comparison to the wild-type, much lower energy barriers are required for translocation. The expected higher translocation rates were confirmed on the macroscopic scale by liposome-swelling assays. A microscopic view on the millisecond timescale was obtained by analysis of temperature-dependent ion current fluctuations in the presence of ampicillin and provide the enthalpic part of the energy barrier. By studying antibiotic translocation over various timescales and length scales, we were able to discern its molecular mechanism and rate-limiting interactions, and draw biologically relevant conclusions that may help in the design of drugs with enhanced permeation rates.
我们在这项研究中的目的是为氨苄青霉素通过 OmpF 的转运提供一个原子水平的描述。OmpF 是大肠杆菌的主要外膜通道，也是β-内酰胺类抗生素的主要进入点。通过应用元动力学模拟，我们还获得了扩散途径中的能量势垒。然后，我们研究了影响通道收缩区电荷和大小的突变的影响，结果发现与野生型相比，转运所需的能量势垒要低得多。通过脂质体肿胀测定在宏观尺度上证实了预期的更高的转运速率。通过在存在氨苄青霉素的情况下分析温度依赖性离子电流波动，在毫秒时间尺度上获得了一个微观视角，并提供了能量势垒的焓部分。通过研究不同时间尺度和长度尺度上的抗生素转运，我们能够辨别其分子机制和限速相互作用，并得出具有生物学意义的结论，这可能有助于设计具有更高渗透速率的药物。
