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. 1999 Apr;67(4):1806–1811. doi: 10.1128/iai.67.4.1806-1811.1999

TABLE 5.

Effects of multiple mutations on DtxR activity

DtxR construct	DH5α(pCMZ100)		SG22098(pTXZ184)
DtxR construct	β-Galacto-sidase activity^a,c	DtxR quanti-tation^b	β-Galacto-sidase activity^a,c	DtxR quanti-tation^b
pWKS30	32 ± 2.5	0	42 ± 1.0	0
dtxR-7	<0.01	100	2.3 ± 1.0	100
H79A/E83A	31 ± 4.5	0	39 ± 6.6	0
H79A/H98A	ND^d	0	36 ± 6.4	0
H98A/E83A	9.2 ± 2.6	64	1.6 ± 1.8	100
N130A/S126A	28 ± 4.6	ND	26 ± 3.6	ND
R80A/H79A/H98A	40 ± 2.4	58	33 ± 6.4	67
H79A/E20A/R80A	36 ± 3.2	56	28 ± 12.3	67
R80A/H98A/E83A	19 ± 2.5	67	11 ± 1.5	88

^a

β-Galactosidase activities are given as Miller units.

^b

Quantities of DtxR variants are given as percentages of the expression of wild-type DtxR.

^c

Assays were performed in triplicate with three separate cultures; mean values ± standard deviations are given.

^d

ND, not determined.