TABLE 3.
Effects of single mutations within DtxR
| DtxR construct | DH5α(pCMZ100)
|
SG22098(pTXZ184)
|
||
|---|---|---|---|---|
| β-Galacto-sidase activitya,c | DtxR quanti-tationb | β-Galacto-sidase activitya,c | DtxR quanti-tationb | |
| Controls | ||||
| pWKS30 | 32 ± 2.5 | 0 | 42 ± 1.0 | 0 |
| dtxR-7 | <0.01 | 100 | 2.3 ± 1.0 | 100 |
| Site 1 metal-coordi-nating ligandsd | ||||
| H79A | 8.2 ± 0.9 | 78 | 4.3 ± 2.9 | 94 |
| E83A | 11 ± 0.5 | 67 | 10 ± 0.6 | 94 |
| H98A | 5.4 ± 1.8 | 82 | 2.9 ± 1.7 | 98 |
| Site 2 metal-coordi-nating ligandsd | ||||
| C102A | 35 ± 5.7 | 67 | 33 ± 0.1 | 69 |
| E105A | 27 ± 2.7 | 100 | 25 ± 6.5 | 86 |
| H106A | 32 ± 1.7 | 100 | 34 ± 5.8 | 92 |
| Site 1 anion-coordi-nating ligands | ||||
| R80A | 23 ± 4.9 | 60 | 20 ± 2.0 | 93 |
| S126A | 20 ± 2.1 | 54 | 14 ± 2.6 | 91 |
| N130A | 23 ± 2.6 | 49 | 19 ± 1.7 | 73 |
a
β-Galactosidase activities are given as Miller units.
b
Quantities of the 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
These amino acid substitutions have been analyzed previously (3) but were included in this analysis as controls.