Structural insights into H+-coupled multidrug extrusion by a MATE transporter

Area of Science:

• Structural biology
• Biochemistry
• Molecular biology

Background:

• Multidrug and toxic compound extrusion (MATE) transporters are crucial for cellular defense against xenobiotics.
• They mediate drug efflux by coupling to ion gradients (Na(+) or H(+)), contributing to multidrug resistance.
• Previous structures of Na(+)-coupled MATE transporters (NorM subfamily) showed quasi-two-fold symmetry.

Purpose of the Study:

• To determine the structure of an H(+)-coupled MATE transporter, DinF from Bacillus halodurans.
• To elucidate the transport mechanism of DinF and compare it with known MATE transporters.
• To investigate the structural basis for substrate binding and ion/substrate competition.

Main Methods:

• X-ray crystallography to determine the 3.2-Å resolution structure of DinF.
• Biochemical analyses to identify the substrate-binding chamber and investigate transport mechanisms.
• Comparative structural analysis with other MATE transporters.

Main Results:

• The crystal structure revealed a unique asymmetric arrangement of 12 transmembrane helices in DinF.
• A membrane-embedded substrate-binding chamber was identified through crystallographic and biochemical data.
• Evidence suggests direct competition between H(+) and substrate during DinF transport.
• A model for alternating access conformational changes driving multidrug extrusion was proposed.

Conclusions:

• H(+)-coupled MATE transporters exhibit distinct structural features and mechanisms compared to their Na(+)-coupled counterparts.
• The asymmetric structure of DinF and its proposed transport mechanism highlight mechanistic diversity within the MATE transporter superfamily.
• These findings advance our understanding of multidrug resistance and transporter function.