Table 4.

Repression by mutant LexA-Mig1 proteins

Expressed proteinInvertase activityaβ-Galactosidase activityb with:Fold repression
0lexA operators4 lexA operators
LexA87 833221512.1
LexA-Mig14244830
LexA-Mig1S278*S311*6NDc NDND
LexA-Mig1S222*S278*S311*85472522
LexA-Mig1S278*S311*S381*74312121
  • a YM4738 (mig1Δ mig2Δ) was transformed with plasmids expressing the indicated LexA fusion protein. The double mutant produces higher invertase activity than amig1Δ single mutant, thereby providing a more sensitive assay for Mig1 repressor function. Transformants were grown to mid-log phase in SC medium plus 5% glucose and assayed for invertase activity (expressed as micromoles of glucose released per minute per 100 mg of cells).

  • b Wild-type strain MCY829 was transformed with plasmids expressing the indicated LexA fusion protein andlexAop-CYC1-lacZ reporters with zero or four lexAoperators (pLGΔ312S, JK1621). Transformants were grown in SC medium plus 5% glucose. β-Galactosidase activity (Miller units) was assayed in permeabilized cells. Values represent the averages from at least three transformants. Standard errors were <18%.

  • c ND, not determined.