Identification of key residues for efficient glucose transport by the hexose transporter CgHxt4 in high sugar fermentation yeast Candida glycerinogenes.

Efficient hexose transporters are essential for the development of industrial yeast strains with high fermentation performance. We previously identified a hexose transporter, CgHxt4, with excellent sugar uptake performance at ultra-high glucose concentrations (200 g/L) in the high sugar fermenting yeast C. glycerinogenes. To understand the working mechanism of this transporter, we constructed 87 mutants and examined their glucose uptake performance. The results revealed that five residues (N321, N322, F325, G426, and P427) are essential for the efficient glucose transport of CgHxt4. Subsequently, we focused our analysis on the roles of N321 and P427. Specifically, N321 and P427 are likely to play a role in glucose coordination and conformational flexibility, respectively. Our results help to expand the application potential of this transporter and provide insights into the working mechanism of yeast hexose transporter. KEY POINTS: • Five residues, transmembrane segments 7 and 10, were found to be essential for CgHxt4. • N321 and P427 are likely to play a role in glucose coordination and conformational flexibility, respectively. • Chimeric CgHxt5.4TM7 significantly enhanced the performance of CgHxt5.