TABLE 1.
E. coli proteins with known functions induced during the SOS response
| Gene | Gene product/function | No. of copies/cella
|
Increase in expressionb | Strength of SOS boxc/LexA affinityd | |
|---|---|---|---|---|---|
| Basal level | SOS-induced cells | ||||
| Expressed first | |||||
| lexA | LexA/SOS repressor | 1,300 | 1e | 5.8 | 6.4 and 8.3/15 |
| uvrA | UvrABC excinuclease/excision repair | 20 | 250 | 4.8 | 7.0/14.6 |
| uvrB | UvrABC excinuclease/excision repair | 250 | 1,000 | 3.7 | 6.1/8.8 |
| uvrD | Helicase II/excision repair, fidelity of recombinational repair | 5,000–8,000 | 25,000–65,000 | 5.9 | 8.8/17.9 |
| polB | DNA polymerase II/translesion DNA synthesis | 40 | 300 | 7.3 | 12.1/?f |
| ruvA | Subunit of RuvAB helicase/recombinational repair | 700 | 5,600 | 2–3 | 9.2/? |
| ruvB | Subunit of RuvAB helicase/recombinational repair | 200 | 1,600 | See ruvA | See ruvA |
| dinI | Inhibition of UmuD processing | <500 | 2,300 | ? | ? |
| Expressed second | |||||
| recA | RecA coprotease, synaptase/SOS derepressor, recombinational repair | 1,000–10,000 | 100,000 | 12.0 | 4.3/3.8 |
| recN | RecN/recombinational repair | ? | ? | 10 | 4.2 and 9.4/? |
| Expressed last | |||||
| sfiA | SfiA (SulA)/cell division inhibitor | ? | ? | 125 | 4.7/1 |
| umuD | Subunit of UmuD′C/translesion DNA synthesis | 180 | 2,400 | 22.5 | 2.8/1.1 |
| umuC | Subunit of UmuD′C/translesion DNA synthesis | 0 | 200 | ? | See umuD |
| Apoptosis | |||||
| cea | Colicin E1 | ? | ? | ? | 7.6 and 11.6/? |
| caa | Colicin A | ? | ? | ? | 9.6 and 11.5/? |
Sources for the protein copy number and its SOS increase: LexA, 558; UvrA and UvrB, 693; UvrD, 305 and 330; PolB, 58 and 503; RuvAB, 590, Benson and West (unpublished), cited in reference 721; DinI, 753; RecA, 292 and 543; RecN, 494; UmuD and UmuC, 742.
Increase in expression is given as the ratio of the gene expression without LexA repression to the gene expression with full repression, both measured as β-galactosidase activity. Except for ruvA and recN, the values are averages of two measurements done at 30°C and 42°C (563).
The strength of the SOS box in the promoter region of a gene is represented by the heterology index. Higher values reflect more deviations from the SOS box consensus and hence weaker LexA binding. The data are from reference 356.
LexA affinity is expressed as relative LexA affinity in vitro compared to the affinity to the sfiA operator. Higher values mean weaker LexA binding, while lower values mean stronger LexA binding. The data are from reference 563.
LexA protein is degraded during the SOS induction.
?, not known.