title: Three Agt1 transporters from brewer's yeasts exhibit different temperature dependencies for maltose transport over the range of brewery temperatures (0–20 °C).
abstract: Zero-trans rates of maltose transport by brewer's yeasts exert strong control over fermentation rates and are strongly temperature-dependent over the temperature range (20–0 °C) of brewery fermentations. Three α-glucoside transporters, ScAgt1(A60) (a Saccharomyces cerevisiae version of Agt1 from an ale strain), ScAgt1-A548V (a variant of ScAgt1(A60) with a single amino acid change in a transmembrane domain), and SbAgt1 (a Saccharomyces (eu)bayanus version from a lager strain), were compared. When expressed in the same laboratory yeast, grown at 24 °C and assayed at 0, 10, and 20 °C, SbAgt1 had the lowest absolute maltose uptake activity at 20 °C but smallest temperature dependence, ScAgt1-A548V had the highest activity but greatest temperature dependence, and ScAgt1(A60) had intermediate properties. ScAgt1(A60) exhibited higher absolute rates and smaller temperature dependencies when expressed in laboratory rather than brewer's strains. Absolute rates closely reflected the amounts of GFP-tagged ScAgt1(A60) transporter in each host's plasma membrane. Growth at 15 °C instead of 24 °C decreased the absolute activities of strains expressing ScAgt1(A60) by two- to threefold. Evidently, the kinetic characteristics of at least ScAgt1(A60) depended on the nature of the host plasma membrane. However, no consistent correlation was observed between transport activities and fatty acid or ergosterol compositions.
authors.forename: Virve
authors.initials: V
authors.lastname: Vidgren
authors.forename: Kaarina
authors.initials: K
authors.lastname: Viljanen
authors.forename: Laura
authors.initials: L
authors.lastname: Mattinen
authors.forename: Jari
authors.initials: J
authors.lastname: Rautio
authors.forename: John
authors.initials: J
authors.lastname: Londesborough
mesh_terms: D008320:Maltose / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D012440:Saccharomyces / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000528:radiation effects*; D013696:Temperature
chemical_list: D009004:Monosaccharide Transport Proteins; D008320:Maltose