Small is mighty: EmrE, a multidrug transporter as an experimental paradigm

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• EmrE is a small multidrug transporter found in Escherichia coli.
• It functions as a homooligomer, a unique characteristic for transporters of its kind.
• The transporter possesses four transmembrane segments and a single membrane-embedded charged residue per monomer.

Purpose of the Study:

• To elucidate the structural basis of EmrE's transport mechanism.
• To understand the role of the membrane-embedded charged residue in substrate and proton coupling.

Main Methods:

• Structural analysis of EmrE.
• Biochemical assays to study substrate and proton binding.

Main Results:

• EmrE monomers assemble into a functional homooligomer.
• A key charged residue is integral to the binding site.
• This residue facilitates a "time-shared" binding mechanism for both substrates and protons.

Conclusions:

• The unique structure of EmrE, particularly the charged residue, is crucial for its function as a multidrug transporter.
• The "time-shared" binding site mechanism explains the coupling of substrate transport and proton movement.