Structural characterization of the Aspergillus niger citrate transporter CexA uncovers the role of key residues S75, R192 and Q196.

ABSTRACT: The Aspergillus niger CexA transporter belongs to the DHA1 (Drug-H⁺ antiporter) family. CexA homologs are exclusively found in eukaryotic genomes, and CexA is the sole citrate exporter to have been functionally characterized in this family so far. In the present work, we expressed CexA in Saccharomyces cerevisiae, demonstrating its ability to bind isocitric acid, and import citrate at pH 5.5 with low affinity. Citrate uptake was independent of the proton motive force and compatible with a facilitated diffusion mechanism. To unravel the structural features of this transporter, we then targeted 21 CexA residues for site-directed mutagenesis. Residues were identified by a combination of amino acid residue conservation among the DHA1 family, 3D structure prediction, an

SUBMITTER: Alves J 

PROVIDER: S-EPMC10196274 | biostudies-literature | 2023

REPOSITORIES: biostudies-literature