James Chloë E, Mahendran Kozhinjampara R, Molitor Alexander, Bolla Jean-Michel, Bessonov Andrey N, Winterhalter Mathias, Pagès Jean-Marie
UMR-MD-1, Transporteurs membranaires, Chimiorésistance et Drug Design, Faculté de Médecine, IFR 88, Université de la Méditerranée, Marseille, France.
PLoS One. 2009;4(5):e5453. doi: 10.1371/journal.pone.0005453. Epub 2009 May 12.
Multi-drug resistant (MDR) infections have become a major concern in hospitals worldwide. This study investigates membrane translocation, which is the first step required for drug action on internal bacterial targets. beta-lactams, a major antibiotic class, use porins to pass through the outer membrane barrier of Gram-negative bacteria. Clinical reports have linked the MDR phenotype to altered membrane permeability including porin modification and efflux pump expression.
METHODOLOGY/PRINCIPAL FINDINGS: Here influx of beta-lactams through the major Enterobacter aerogenes porin Omp36 is characterized. Conductance measurements through a single Omp36 trimer reconstituted into a planar lipid bilayer allowed us to count the passage of single beta-lactam molecules. Statistical analysis of each transport event yielded the kinetic parameters of antibiotic travel through Omp36 and distinguishable translocation properties of beta-lactams were quantified for ertapenem and cefepime. Expression of Omp36 in an otherwise porin-null bacterial strain is shown to confer increases in the killing rate of these antibiotics and in the corresponding bacterial susceptibility.
CONCLUSIONS/SIGNIFICANCE: We propose the idea of a molecular "passport" that allows rapid transport of substrates through porins. Deciphering antibiotic translocation provides new insights for the design of novel drugs that may be highly effective at passing through the porin constriction zone. Such data may hold the key for the next generation of antibiotics capable of rapid intracellular accumulation to circumvent the further development MDR infections.
多重耐药（MDR）感染已成为全球医院的主要关注点。本研究调查膜转运，这是药物作用于细菌内部靶点的第一步。β-内酰胺类是一类主要的抗生素，通过孔蛋白穿过革兰氏阴性菌的外膜屏障。临床报告已将MDR表型与膜通透性改变联系起来，包括孔蛋白修饰和外排泵表达。
方法/主要发现：在此对β-内酰胺类通过产气肠杆菌主要孔蛋白Omp36的流入进行了表征。通过重构到平面脂质双分子层中的单个Omp36三聚体进行的电导测量使我们能够计数单个β-内酰胺分子的通过情况。对每个转运事件的统计分析得出了抗生素通过Omp36的动力学参数，并对厄他培南和美罗培南的β-内酰胺类可区分的转运特性进行了量化。在其他方面缺乏孔蛋白的细菌菌株中Omp36的表达显示出这些抗生素的杀伤率和相应细菌敏感性的增加。
结论/意义：我们提出了一种分子“护照”的概念，它允许底物通过孔蛋白快速转运。解读抗生素转运为设计可能在穿过孔蛋白收缩区时非常有效的新型药物提供了新的见解。这些数据可能是下一代能够快速在细胞内积累以规避MDR感染进一步发展的抗生素的关键。
