TABLE 3.

Effects of alanine substitutions in CRP AR1 and AR2 at Φ(rhaB-lacZ)

CRP derivative	Φ(rhaB-lacZ)Δ226		Φ(rhaB-lacZ)Δ110
	β-Gal sp acta	% wt	β-Gal sp act	% wt
wt	1,018	100	812	100
T158A	1,051	103	684	84
G162A	532	52	466	57
H19A	912	90	382	47
H21A	418	41	356	44
K101A	733	72	631	77

^aβ-Galactosidase (β-Gal) specific activity was measured from single-copy rhaB-lacZ fusions in crp deletion strains transformed with plasmids encoding either a wild-type (wt) or substitution derivative of CRP. Cultures were grown in MOPS growth media containing glycerol, l-rhamnose, and 125 μg of ampicillin per ml. Standard errors were less than 27% of the average units.