Table 2. Effects of mutations at domain interface of PhoP and of the DNA sequences on PhoP-DNA binding measured by ITC.

Sequence	PhoP	Kd, nM	ΔH, kcal/mol	Nb
DRacgatTCACAGCtgatTCACAGCatctacg	wtY205AL113D	19.2 ± 2.821.8 ± 6.226.2 ± 6.5	−14.2 ± 0.1−18.2 ± 0.2−19.4 ± 0.1	0.460.510.50
hisGcgcgaccCgCAGCatgcTCACAGCtttcga	wtY205AL113D	35.6 ± 4.3114.5 ± 11.2116.6 ± 11.7	−14.5 ± 0.1−16.2 ± 0.1−15.8 ± 0.1	0.480.480.44
ahpCtttgccTgACAGCgactTCACgGCacgatg	wtY205AL113D	103.8 ± 7.2653.6 ± 57.2595.2 ± 51.4	−13.0 ± 0.1−16.4 ± 0.3−15.1 ± 0.2	0.500.450.43
lpqAgcacctTCACcGCccgccCACAGCcacgca	wtY205AL113D	347.2 ± 35.13076.9 ± 371.12873.6 ± 540.9	−8.31 ± 0.08−13.8 ± 0.7−10.3 ± 0.9	0.510.430.39
DRs3aagtaccTCACAGCactTCACAGCtttcat	wtL113D	432.9 ± 17.5367.6 ± 52.2	−12.7 ± 0.7−11.8 ± 0.2	0.500.47
trigtaccTCACAGCacttTCACAGCtttcTCACAGCatctatg	wt	4.6 ± 2.7	−11.5 ± 0.2	0.30
tetragtaccTCACAGCacttTCACAGCtttcTCACAGCtgatTCACAGCatctatg	wt	2.2 ± 0.7	−14.8 ± 0.1	0.21
RD6aagtaccTCACAGCacttTCACAGCtttcat	PhoPC	188 ± 9	−18.9 ± 0.1	0.49
RD6-halfcagaagTCACAGCacttggg	PhoPC	12.2 ± 1.6μMc	−3.46 ± 0.42	0.62

^aBoth DR and RD6 are perfect direct-repeat sequences with a 4-bp spacer. DRs3 has the same repeated motifs but with a 3-bp spacer.

^bN is the stoichiometry, referring to the copy number of DNA per PhoP molecule, derived from fitting of the ITC data.

^cBinding dissociation constants of >10 μM cannot be reliably measured because of the small binding heat.