Table 1.
The effects of tri-alanine substitutions of σ70 R4 on SoxS-dependent transcription activation of class I and class II promoters.
| Tri-Alanine Stretches of σ70 R4 | β-galactosidase activity (% of wild type) | |||||
|---|---|---|---|---|---|---|
| Class I Promoters | Class II Promoters | |||||
| fpr | mar | zwf | fumC | inaA | micF | |
| P531A-D533A | 127 ±5 | 127 ±9 | 93 ±4 | 123 ±13 | 102 ±5 | 102 ±4 |
| S534A-T536A | 126 ±8 | 97 ±9 | 109 ±6 | 102 ±8 | 110 ±3 | 98 ±11 |
| T537A-S539A | 88 ±6 | 88 ±5 | 98 ±8 | 156 ±4 | 86 ±12 | 93 ±6 |
| L540A-A542A | 116 ±9 | 112 ±8 | 97 ±5 | 104 ±8 | 116 ± 8 | 104 ±4 |
| A543A-H545A | 112 ±8 | 97 ±9 | 93 ±6 | 105 ±10 | 105 ±6 | 106 ±3 |
| D546A-L548A | 120 ±4 | 97 ±5 | 89 ±7 | 85 ±6 | 113 ±4 | 116 ±9 |
| A549A-L551A | 127 ±5 | 86 ±6 | 99 ±4 | 98 ±12 | 114 ±2 | 113 ±8 |
| T552A-R554A | 123 ±5 | 85 ±5 | 69 ±4 | 149 ±18 | 100 ±8 | 86 ±4 |
| E555A-K557A | 116 ± 3 | 77 ±5 | 83 ±5 | 93 ±12 | 83 ±2 | 89 ±8 |
| V558A-R560A | 109 ±3 | 83 ±8 | 84 ±10 | 101 ±11 | 92 ±4 | 111 ±10 |
| M561A-F563A | 78 ±7 | 84 ±7 | 115 ±5 | 154 ±8 | 105 ±5 | 116 ±8 |
| G564A-D566A | 87 ±8 | 91 ±9 | 86 ±2 | 158 ±7 | 120 ±12 | 108 ±6 |
| M567A-T569A | 101 ±8 | 83 ±6 | 70 ±1 | 134 ±15 | 113 ±7 | 112 ±7 |
| D570A-T572A | 89 ±9 | 95 ±4 | 83 ±2 | 121 ±16 | 130 ±13 | 88 ±7 |
| L573A-E575A | 70 ±4 | 79 ±7 | 101 ±2 | 159 ±14 | 90 ±3 | 91 ±3 |
| V576A-K578A | 78 ±6 | 83 ±7 | 69 ±1 | 95 ±8 | 151 ±14 | 131 ±4 |
| Q579A-D581A | 119 ±14 | 69 ±8 | 76 ±2 | 95 ±8 | 113 ±2 | 126 ±5 |
| V582A-R584A | 109 ±5 | 74 ±8 | 85 ±2 | 89 ±8 | 96 ±5 | 98 ±4 |
| E585A-I587A | 112 ± 2 | 85 ±5 | 85 ±1 | 88 ±3 | 101 ±3 | 121 ±5 |
| R588A-I590A | 70 ±5 | 88 ±9 | 91 ±3 | 104 ±7 | 138 ±8 | 127 ±12 |
The library of tri-alanine substitutions of σ70 R4 carried on plasmid pVR-σ70 was introduced into derivatives of E. coli strain N7840 (Δmor) [pBAD33-his6-SoxS] carrying transcriptional fusions of the above-named promoters to lacZ. SoxS expression was induced with 0.2% arabinose when the A600 reached 0.1–0.2; wild type and mutant σ70 proteins are constitutively expressed from a truncated galP1 promoter carried on plasmid pVR-σ70. The host chromosome contains rpoD and expresses wild type σ70 from it. Expression of the fusions was determined by assay of β-galactosidase activity as described in Materials and Methods. The data are expressed as the % of the wild type value and the standard deviations are given as the % of the mean. Wild type Miller units at SoxS dependent promoters were fpr (2110), mar (2980), zwf (2450), fumC (1196), inaA (1601) and micF (443). As described in the text, values for mutants that are ≤ 80% of the wild type activity are taken as a meaningful difference; these values are in bold and are highlighted in grey.