Molecular mechanism of substrate recognition and transport by the AtSWEET13 sugar transporter

Significance The Sugar Will Eventually be Exported Transporter (SWEET) family of sugar transporters can discriminate and transport mono- and disaccharides. Using X-ray crystallography methods, we determined the structure of AtSWEET13 from Arabidopsis thaliana complexed with a substrate analog 2′-deoxycytidine 5′-monophosphate. Based on the structural study and in-cell transport activity analysis, key amino acid residues important for substrate recognition and selectivity were identified. A mechanism for substrate selectivity based on the size of the central cavity is proposed.