Structural basis for dual-mode inhibition of the ABC transporter MsbA

Abstract

The movement of core-lipopolysaccharide across the inner membrane of Gram-negative bacteria is catalysed by an essential ATP-binding cassette transporter, MsbA. Recent structures of MsbA and related transporters have provided insights into the molecular basis of active lipid transport; however, structural information about their pharmacological modulation remains limited. Here we report the 2.9 Å resolution structure of MsbA in complex with G907, a selective small-molecule antagonist with bactericidal activity, revealing an unprecedented mechanism of ABC transporter inhibition. G907 traps MsbA in an inward-facing, lipopolysaccharide-bound conformation by wedging into an architecturally conserved transmembrane pocket. A second allosteric mechanism of antagonism occurs through structural and functional uncoupling of the nucleotide-binding domains. This study establishes a framework for the selective modulation of ABC transporters and provides rational avenues for the design of new antibiotics and other therapeutics targeting this protein family.

Single-Unit Imaging of Membrane Protein-Embedded Nanodiscs from Two Oriented Sides by High-Speed Atomic Force Microscopy

“…This method can be used for the dynamic imaging of other membrane proteins with a large cytoplasmic region, such as ABC transporters and receptor tyrosine kinases (Endres et al, 2014;Thomas and Tampe, 2018). Moreover, drastic conformational transitions in the soluble domains of membrane proteins could be inferred from static snapshots obtained by crystallography and electron micrography (Gutmann et al, 2018;Ho et al, 2018;Menting et al, 2013;Mi et al, 2017), and real-time movies such as HS-AFM observation provide complementary dynamic information regarding the molecular mechanism underlying membrane protein functions. In addition, this method can be applied to elucidate the dynamics of inherently disordered soluble regions of membrane proteins.…”

Countering Gram-Negative Antibiotic Resistance: Recent Progress in Disrupting the Outer Membrane with Novel Therapeutics

“…Recently, two compounds that are active against MsbA were reported. A quinoline compound, G907, is an optimized and potent inhibitor of E. coli MsbA in vitro [83]. G907 prevents the ATPase activity of MsbA by binding the transmembrane pocket of the MsbA homodimer to lock the protein in a cytosol-facing LPS-bound state [83].…”

Structural features underlying recognition and translocation of extracellular polysaccharides

“…The lipid-A-core oligosaccharide complex (often referred to as lipid-A-Kdo2) is synthesized on the membrane's cytosolic side and transported to the periplasmic leaflet by the MsbA ABC transporter. Recent cryo-electron microscopy structures of MsbA bound to a lipid-A-Kdo2 molecule provided important insights into its translocation mechanism [57,58]. On the cytosolic side, the glycolipid binds in a deep pocket with its acyl chains pointing towards the periplasm.…”