TABLE 4.

Maltose induction of MAL gene expression in strains carrying mutations in the C-terminal cytoplasmic domain of Mal61/HA maltose permeasea

MAL61/HA alleleMaltose fermentationbMaltase activitycMaltose transport activitydRelative level of Mal61/HA protein
MAL61/HA+2,2315.45100
MAL61/HA-581NS+2,1172.6879
MAL61/HA-575NS+1,5820.6341
MAL61/HA-570NS690.06<1
MAL61/HA-560NS770.06<1
MAL61/HA571-580)7020.3132
Vector control420.06<1
  • a Strain CMY1050 was transformed with a plasmid carrying the indicated MAL61/HA allele in vector pUN30. Cells were grown in selective induced medium with 3% glycerol, 2% lactate, and 2% maltose to mid-log phase. Fermentation was determined as described in Table 3, footnote a. Maltase activity and maltose transport activity were determined as described in Materials and Methods. The relative levels of Mal61/HA permease protein were determined by comparison of Western blots using total cell extracts from cells grown under maltose-induced conditions.

  • b +, maltose fermented; −, maltose not fermented.

  • c Expressed as nanomoles of PNPG hydrolyzed per milligram of total protein per minute.

  • d Expressed as nanomoles of maltose transported per milligram of cells per minute.