TABLE 3.

Function of phoU mutants

Plasmid or mutationa	Signal transduction activityb		Growth yield (% of wild-type growth)c
	Activity (AP units) (avg ± SD)	% Activity
pKG116	478.8 ± 28.3	0	67.8
p116phoU	4.9 ± 0.2	100	100
p116phoU2	5.0 ± 0.3	100	100
M26I	32.65 ± 0.4	94.2	91.5
P81S	120.61 ± 4.6	75.6	74.5
A83T	29.78 ± 1.0	94.8	91.1
D85G	73.29 ± 4.6	85.6	86.4
K94E	20.0 ± 0.2	96.8	91.3
L99P	577.3 ± 6.2	−20.8	74.5
C206R	12.3 ± 0.3	98.5	91.7
C206Y	21.12 ± 9.1	96.6	90.0

^aThe designations for the mutations indicate the amino acid in the wild-type PhoU sequence, followed by the residue number and the mutant residue. The mutant PhoU proteins were encoded in the p116phoU plasmid background and contained an additional V126A mutation.

^bEach of the plasmids was transformed into the BM252 strain, and fresh colonies were grown in 5 ml LB medium containing ampicillin, chloramphenicol, and 200 μM IPTG. The AP activities are the averages ± standard deviations of three separate trials. The percent activity was calculated using the following formula: [(AP activity of pKG116 − AP activity of sample) × 100]/(AP activity of pKG116 − AP activity of p116phoU2).

^cThe growth yield was calculated by culturing the strains overnight to stationary phase and determining the OD₆₀₀ for each culture. The value for a strain encoding wild-type PhoU was determined as follows: (OD₆₀₀ of mutant × 100)/OD₆₀₀ of BM255.