Bacterial Outer Membrane Porins as Electrostatic Nanosieves: Exploring Transport Rules of Small Polar Molecules
Bacterial Outer Membrane Porins as Electrostatic Nanosieves: Exploring Transport Rules of Small Polar Molecules
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DOI：
10.1021/acsnano.6b08613
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发表时间：
2017-06-01
期刊：
影响因子：
17.1
通讯作者：
Ceccarelli, Matteo
中科院分区：
文献类型：
--
作者：
Bajaj, Harsha;Gutierrez, Silvia Acosta;Ceccarelli, Matteo
分子通过生物膜的运输是生物学中的一个基本过程，通过选择性通道和一般的孔来促进。革兰氏阴性细菌中一些外膜孔的结构，与其他真核生物的孔一样，表明它们是静电调节的纳米筛设备的原型。在本研究中，我们使用诺氟沙星作为单分子电生理学中的偶极探针，检测了大肠杆菌最丰富的两个外膜通道的内部静电。诺氟沙星与这些纳米通道相互作用的结合速率常数与电压的依赖关系遵循指数趋势，对于中性分子来说这是意想不到的。我们结合电生理学、通道突变和增强采样分子动力学模拟来解释这一分子机制。电压和温度相关的离子电流测量使我们能够量化通道内的横向电场以及外加电位下降的距离。最后，我们提出了极性分子通过这些静电纳米筛的传输的一般模型。我们的模型有助于进一步了解革兰氏阴性病原体的渗透性基础，有助于填补过去20年来限制有效抗生素发现的创新空白。
Transport of molecules through biological membranes is a fundamental process in biology, facilitated by selective channels and general pores. The architecture of some outer membrane pores in Gram-negative bacteria, common to other eukaryotic pores, suggests them as prototypes of electrostatically regulated nanosieve devices. In this study, we sensed the internal electrostatics of the two most abundant outer membrane channels of Escherichia coli, using norfloxacin as a dipolar probe in single molecule electrophysiology. The voltage dependence of the association rate constant of norfloxacin interacting with these nanochannels follows an exponential trend, unexpected for neutral molecules. We combined electrophysiology, channel mutagenesis, and enhanced sampling molecular dynamics simulations to explain this molecular mechanism. Voltage and temperature dependent ion current measurements allowed us to quantify the transversal electric field inside the channel as well as the distance where the applied potential drops. Finally, we proposed a general model for transport of polar molecules through these electrostatic nanosieves. Our model helps to further understand the basis for permeability in Gram-negative pathogens, contributing to fill in the innovation gap that has limited the discovery of effective antibiotics in the last 20 years.