Tetrahydrofolate recognition by the mitochondrial folate transporter

Area of Science:

• Biochemistry
• Molecular Biology
• Membrane Transport

Background:

• Mitochondrial carrier family (MCF) proteins transport small molecules across the inner mitochondrial membrane.
• MCF proteins share conserved motifs, but the mitochondrial folate transporter (MFT) has a unique tryptophan residue.
• The function of this MFT-specific tryptophan (Trp-142) and other residues in folate transport is not well understood.

Purpose of the Study:

• To investigate the role of specific amino acid residues, including Trp-142, in the function of the mammalian mitochondrial folate transporter (MFT).
• To elucidate the mechanism by which MFT interacts with and transports tetrahydrofolate.

Main Methods:

• Molecular dynamics simulations of MFT in a membrane environment to identify key interacting residues.
• Site-directed mutagenesis to probe the function of identified residues in folate transport.
• Cell viability assays to assess the impact of mutations on MFT function.

Main Results:

• Molecular dynamics simulations revealed sequential interactions involving Trp-142 and other residues that coordinate tetrahydrofolate movement.
• Mutating residues identified by simulations severely impaired folate transport.
• Mutation of MFT Trp-142 to the consensus MCF residue (W142D) was lethal, indicating its essential role.

Conclusions:

• MFT Trp-142 and other interior residues are critical for coordinating tetrahydrofolate transport and substrate positioning.
• These residues are involved in substrate recognition and binding within the MFT transport cavity.
• The unique MFT Trp-142 is essential for MFT function and cell survival.