Outward open conformation of a Major Facilitator Superfamily multidrug/H+ antiporter provides insights into switching mechanism

Kumar Nagarathinam,Tohru Terada,Narinobu Juge,Yoshiko Nakada-Nakura,Milton T Stubbs,Christoph Parthier,Frank Jaenecke,Yunhon Hotta,Takaaki Miyaji,Hiroshi Omote,Kehong Liu,Mikio Tanabe,So Iwata,Norimichi Nomura

doi:10.1038/s41467-018-06306-x

Abstract

Multidrug resistance (MDR) poses a major challenge to medicine. A principle cause of MDR is through active efflux by MDR transporters situated in the bacterial membrane. Here we present the crystal structure of the major facilitator superfamily (MFS) drug/H+ antiporter MdfA from Escherichia coli in an outward open conformation. Comparison with the inward facing (drug binding) state shows that, in addition to the expected change in relative orientations of the N- and C-terminal lobes of the antiporter, the conformation of TM5 is kinked and twisted. In vitro reconstitution experiments demonstrate the importance of selected residues for transport and molecular dynamics simulations are used to gain insights into antiporter switching. With the availability of structures of alternative conformational states, we anticipate that MdfA will serve as a model system for understanding drug efflux in MFS MDR antiporters.

Highlights

Multidrug resistance (MDR) poses a major challenge to medicine
A large number of MDR transporters belong to the Major Facilitator Superfamily (MFS), found in both Gram-positive and -negative organisms[1,2]
With the availability of structures of alternative conformational states, we anticipate that MdfA will serve as a model system for understanding drug efflux in major facilitator superfamily (MFS) MDR antiporters

Summary

Introduction

Multidrug resistance (MDR) poses a major challenge to medicine. A principle cause of MDR is through active efflux by MDR transporters situated in the bacterial membrane. We present the crystal structure of the major facilitator superfamily (MFS) drug/H+ antiporter MdfA from Escherichia coli in an outward open conformation. Changes in relative orientation of the two lobes within the plane of the bilayer (the rocker-switch mechanism4) allow alternating access to the cytoplasmic and extracellular/periplasmic sides of the membrane, facilitating directed transport of substrates across the membrane, with the transporter cycling between outward open (Oo), inward open (Io) and intermediary occluded states[5,6,7]. With the availability of structures of alternative conformational states, we anticipate that MdfA will serve as a model system for understanding drug efflux in MFS MDR antiporters

Methods

Results

Conclusion