Computational analysis of polymorphic residues in maltose and maltotriose transporters of a wild <i>Saccharomyces cerevisiae</i> strain

The metabolism of maltose and maltotriose, the primary sugars in brewing wort, depends on an efficient transport system. However, most <i>Saccharomyces cerevisiae</i> strains transport maltotriose inefficiently, leaving residual α-glucosides in the final product. Proteins involved in maltotriose transport exhibit diverse polymorphic sequences linked to sugar transport efficiency. In this study, a wild <i>S. cerevisiae</i> strain was placed under adaptive selection, resulting in a strain with a 65 and 44% increase in maltose and maltotriose transport rates, respectively. Genes encoding maltose and maltotriose transporters, including <i>MAL</i>x1, <i>MPH</i>x, and <i>AGT</i>1, were detected in both the native and adapted strains. One variant of Mal31p, carrying a polymorphism at position 371 in transmembrane helix 7, was identified. This helix has been reported to have a high likelihood of undergoing polymorphisms. Bioinformatics analysis revealed structural changes affecting substrate interactions and channel dynamics, with the polymorphism conferring greater protein flexibility and reducing electrostatic interactions. These results suggest that the residue at position 371 in maltose and maltotriose transporters is a key element distinct from those previously reported. Additionally, we propose a significant set of polymorphic residues within these transporters potentially resulting from the evolution of these proteins.