Evolutionary mix-and-match with MFS transporters II

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Understanding secondary active transport mechanisms requires identifying substrate and H(+) binding sites.
• The Major Facilitator Superfamily (MFS) is a large, diverse group of transporters with significant clinical importance.
• Sequence diversity within MFS transporters complicates the localization of functional residues.

Purpose of the Study:

• To identify and physically localize residues involved in substrate and H(+) binding within MFS secondary active transport proteins.
• To overcome the challenges posed by MFS sequence diversity in functional site identification.

Main Methods:

• Analysis of crystallographic structures of MFS members to identify common structural features.
• Alignment of inverted triple-helix structural symmetry motifs within MFS N- and C-terminal six-helix bundles.
• Combinatorial alignment of triple-helix motifs to detect functionally homologous positions.

Main Results:

• A common structural feature in MFS proteins is a central hydrophilic cavity surrounded by transmembrane helices.
• Substrate and H(+)-binding sites were found in similar locations across various MFS symporters.
• Evidence suggests a homologous ordered kinetic mechanism for H(+)-coupled MFS symporters.

Conclusions:

• The study successfully located homologous substrate and H(+) binding sites in diverse MFS symporters by aligning structural motifs.
• Findings suggest a conserved mechanism for H(+) coupling and substrate transport across the MFS superfamily.
• This approach aids in understanding the function of clinically relevant MFS transporters.