TABLE 4.

Effects of alanine substitutions in CRP AR1 and AR2 at Φ(rhaB-lacZ)Δ84

CRP derivative	Φ(rhaB-lacZ)Δ84
	β-Gal sp acta	% wt
wt	19	100
T158A	59	313
G162A	33	174
H19A	31	168
H21A	25	134
K101A	23	122

^aβ-Galactosidase (β-Gal) specific activity was measured from a single-copy rhaB-lacZ fusion in a crp deletion strain 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 10% of the average units.