TABLE 3.

Effect of low levels of Ssa on Hap1 activity^a

Concentration (%) of Gal plus Glc	β-Galactosidase activity (Miller units) when grown in the presence of the indicated concentration of dpIX
	GAL1-SSA1					Wild type
	0 μg/ml	0.05 μg/ml	0.25 μg/ml	1.0 μg/ml	4.0 μg/ml	0 μg/ml	0.05 μg/ml	0.25 μg/ml	1.0 μg/ml	4.0 μg/ml
2	1.4 ± 0.1	116 ± 13	445 ± 12	776 ± 27	1,215 ± 148	1.4 ± 0.1	73 ± 11	687 ± 36	703 ± 58	826 ± 40
1 + 1	73 ± 8	219 ± 14	644 ± 89	837 ± 57	1,499 ± 53	1.1 ± 0.1	72 ± 15	558 ± 19	736 ± 27	1,080 ± 138
0.25 + 1.75	205 ± 35	284 ± 34	513 ± 43	915 ± 216	1,314 ± 296	1.0 ± 0.1	59 ± 6	577 ± 11	740 ± 8	729 ± 11

^aYeast wild-type cells or the 5B6 cells (GAL1-SSA1) (Δssa1 Δssa2 Δssa4 pGAL1-SSA1) were grown in medium containing 2% galactose for a high Ssa1 expression level, 1% galactose plus 1% glucose for a low (5 to 10% of high) Ssa expression level, or 0.25% galactose plus 1.75% glucose for a very low (<2% of high) Ssa1 expression level in the presence of the indicated amounts of dpIX. The HEM1 gene was deleted from all these strains to allow the experimental control of heme concentration. β-Galactosidase activities were detected, and data shown are averages (± standard deviations) of at least three independent transformants.