TABLE 6.

Effects of carboxyl-terminus deletions on activation of Rob by dipyridyl^a

Strain	rob coding sequences present (bp)	β-Galactosidase activity (Miller units):		Ratiob	β-Galactosidase activity (Miller units) with 5 mM 4,4"-dipyridyl	Ratiob
		In untreated samples	With 5 mM 2,2"-dipyridyl
M597	None	7.8	18	2.3	13	1.6
M600	1-867 (wild type)	21	392	18.3	149	6.9
M848	1-777	16	19	1.2	21	1.3
M851	1-642	29	23	0.80	25	0.87
M853	1-528	20	15	0.74	18	0.92
M854	1-450	30	32	1.1	19	0.74
M808	1-369	17	18	1.1	24	1.4

^aThe mar sox rob mutant strains carrying the indicated plasmids were grown to early log phase, treated with 0 or 5 mM 2,2"- or 4,4"-dipyridyl for 1 h at 37°C, and assayed for β-galactosidase activity.

^bThat is, the ratio of activities in the cells treated with 2,2"- or 4,4"-dipyridyl to that in the untreated cells.