Table 5.

Effects of coexpressing STE2 alleles on constitutive activation of the pheromone response pathway

STE2 alleles coexpressed		FUS1-lacZ expression (% wild type + α-factor)
		−α-factor	+α-factor
Wild type	Wild type	0.4	100
Wild type	P258L	0.9	128
Wild type	P258F	0.5	103
L236R	Wild type	0.7	123
L236R	P258L	4.6	114
L236R	P258F	7.0	104

The wild-type STE2 gene or the ste2L236R allele, which causes a specific defect in receptor coupling with G proteins, was coexpressed with the wild-type STE2 gene, or the ste2P258L or ste2P258F alleles. These genes were coexpressed from their normal promoters on centromeric plasmids (pRS313 and pRS314 derivatives) in a ste2Δ mfα1Δ mfα2Δ mutant (KBY20) that contained the FUS1-lacZ gene on a plasmid (pSL307). Where indicated, cells were treated 2 h at 30°C with 1 μM synthetic α-factor (+α-factor); β-galactosidase assays were performed to monitor activation of the pheromone response pathway. Values are expressed as a percent of the activity detected with α-factor–treated cells expressing the wild-type STE2 gene. Values shown are the average of at least four independent transformants, each assayed in duplicate; standard errors were 5-30% of the values shown.