Discovery of Inhibitors of the Lipopolysaccharide Transporter MsbA: From a Screening Hit to Potent Wild-Type Gram-Negative Activity
Vishal Verma, Lan Wang, Sharada S. Labadie, Jun Liang, Benjamin D. Sellers, Jian Wang, Liting Dong, Qiuyue Wang, Shuang Zhang, Zhongya Xu, Yexia Zhang, Yanan Niu, Xinxin Wang, John Wai, Michael F. T. Koehler, Huiyong Hu, Mary Kate Alexander, Mireille Nishiyama, Anh Miu, Yiming Xu, Jodie Pang, Anand Kumar Katakam, Michael Reichelt, Cary D. Austin, Hoangdung Ho, Jian Payandeh, Christopher M. Koth
Abstract
The dramatic increase in the prevalence of multi-drug resistant Gram-negative bacterial infections and the simultaneous lack of new classes of antibiotics is projected to result in approximately 10 million deaths per year by 2050. We report on efforts to target the Gram-negative ATP-binding cassette (ABC) transporter MsbA, an essential inner membrane protein that transports lipopolysaccharide from the inner leaflet to the periplasmic face of the inner membrane. We demonstrate the improvement of a high throughput screening hit into compounds with on-target single digit micromolar (μM) minimum inhibitory concentrations against wild-type uropathogenic Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae. A 2.98 Å resolution X-ray crystal structure of MsbA complexed with an inhibitor revealed a novel mechanism for inhibition of an ABC transporter. The identification of a fully encapsulated membrane binding site in Gram-negative bacteria led to unique physicochemical property requirements for wild-type activity.