Department of Biochemistry and Molecular Biology, Gordon Center for Integrative Science, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA.
Department of Biochemistry and Molecular Biology, Gordon Center for Integrative Science, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA.
Structure. 2013 Jan 8;21(1):76-87. doi: 10.1016/j.str.2012.10.014. Epub 2012 Nov 29.
The structure of OmpF porin in complex with three common antibiotics (zwitterionic ampicillin, anionic ertapenem, and di-anionic carbenicillin) was determined using X-ray crystallography. The three antibiotics are found to bind within the extracellular and periplasmic pore vestibules, away from the narrow OmpF constriction zone. Using the X-ray structures as a starting point, nonequilibrium molecular dynamics simulations with an applied membrane voltage show that ionic current through the OmpF channel is blocked with bound ampicillin, but not with bound carbenicillin. The susceptibility of Escherichia coli expressing OmpF mutants to ampicillin and carbenicillin was also experimentally characterized using microbiologic assays. These results show that general diffusion by OmpF porins allows for transfer of molecules with varied charged states and give insights into the design of more efficient antibiotics. A better understanding of this mechanism will shed light on nature's way of devising channels able to enhance the transport of molecules through membranes.
利用 X 射线晶体学技术，确定了 OmpF 孔蛋白与三种常见抗生素（两性离子氨苄西林、阴离子厄他培南和二阴离子羧苄西林）复合物的结构。这三种抗生素被发现结合在细胞外和周质腔的入口处，远离狭窄的 OmpF 收缩区。利用 X 射线结构作为起点，施加膜电压的非平衡分子动力学模拟表明，结合氨苄西林会阻断 OmpF 通道中的离子电流，但结合羧苄西林则不会。使用微生物测定法还实验表征了表达 OmpF 突变体的大肠杆菌对氨苄西林和羧苄西林的敏感性。这些结果表明，OmpF 孔蛋白的一般扩散允许具有不同荷电状态的分子转移，并为设计更有效的抗生素提供了思路。更好地了解这种机制将揭示自然界设计能够增强分子通过膜运输的通道的方式。
