TABLE 4.
Comparison of the R80A and E20A substitutions in DtxR, alone and in combination with each other or with substitutions for other site 1 ligands
| 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 |
| Substitutions for R80 and E20 | ||||
| R80A | 23 ± 4.9 | 60 | 20 ± 2.0 | 93 |
| E20A | 19 ± 3.5 | 53 | 21 ± 2.3 | 72 |
| R80A/E20A | 20 ± 3.5 | 82 | 21 ± 0.5 | 91 |
| Substitutions for R80 and other site 1 ligands | ||||
| R80A/H79A | 26 ± 4.3 | 80 | 30 ± 3.9 | 81 |
| R80A/E83A | 15 ± 2.5 | 81 | 8.5 ± 1.3 | 100 |
| R80A/H98A | 19 ± 1.5 | 81 | 18 ± 5.2 | 91 |
| R80A/S126A | 29 ± 2.6 | 74 | 33 ± 6.3 | 85 |
| R80A/N130A | 23 ± 1.7 | 71 | 21 ± 2.4 | 79 |
| Substitutions for E20 and site 1 ligands | ||||
| E20A/H79A | 30 ± 4.2 | 73 | 31 ± 1.5 | 55 |
| E20A/E83A | 24 ± 2.3 | 76 | 26 ± 2.5 | 92 |
| E20A/H98A | 22 ± 4.7 | 88 | 19 ± 1.6 | 100 |
| E20A/S126A | 30 ± 4.7 | 79 | 40 ± 0.3 | 96 |
| E20A/N130A | 23 ± 4.4 | 74 | 26 ± 4.4 | 90 |
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.