TABLE 3.
Summary of mutant protein functions
| Mutation | RecA protein levelc | UV resistanced | Recombinatione
|
Basal LexA levelf | Cleavageg
|
|||
|---|---|---|---|---|---|---|---|---|
| λred− gam− | Intrachromosomal | LexA | λ CI | UmuD | ||||
| ΔrecA | None | S | NG | <0.07 | ++++ | − | − | − |
| recA+ | ++++ | R | G | 27 | ++ | WT | WT | WT |
| Clefta | ||||||||
| R105K106 | ++++ | R | G | 25 | +++ | S. def | S. def | WT |
| T242R243 | +++ | S+ | G | 0.2 | ++ | WT | Def | − |
| K232E235 | +++ | R | G | 27 | +++ | S. def | Def | Hyper |
| E233N236 | +++ | R | G | 27 | ++ | S. def | WT | WT |
| I102Y103 | ++++ | S | G− | <0.07 | +++ | S. def | Def | Def |
| K280E281K282 | ++++ | R | G | 33 | +++ | S. def | Def | S. def |
| K256Q257 | ++++ | R | G | 2.4 | ++ | WT | Constit | WT |
| K310D311 | ++++ | R | G | 24 | ++ | S. def | Def | WT |
| E285K286 | < | R− | G | 28 | +++ | S. def | S. def | S. def |
| E259Q261 | +++ | R | G | 25 | ++ | WT | Constit | WT |
| Other surfacesb | ||||||||
| E4K8 | ++++ | R | G | 27 | ++ | WT | Def | WT |
| Q16K19 | ++++++ | R | G | 18 | +++ | Def | WT | WT |
| R33D36 | +++ | R | G | 26 | ++ | WT | WT | WT |
| R85E86 | ++++ | R | G | 20 | ++ | WT | WT | WT |
| R176K177 | ++++ | S | NG | <0.07 | ++++ | − | − | − |
| E296K297 | ++ | R | G | 27 | +++ | S. def | WT | WT |
| Q300N304 | ++++ | R− | G | 6.1 | + | Constit | Constit | Constit |
| E314K317 | + | R | G | 26 | ++ | WT | S. def | WT |
| K294E318 | < | R | G | 35 | ++ | WT | S. def | WT |
| K321E325 | ++++ | R | G | 25 | ++ | WT | WT | WT |
Mutations affecting residues in the cleft.
Mutations affecting residues lying on the surface of the filament.
RecA protein levels: <, less than 10% RecA protein relative to wild type (WT); +, 10 to 25% WT; ++, 25 to 50%; +++, 50 to 75%; ++++, 75 to 100%.
UV resistance. Results of the UV sensitivity streak test are shown. R, WT cell growth; R−, slightly sensitive; S, like the ΔrecA control; S+, slightly more resistant than the ΔrecA strain.
Recombination. Growth of λred− gam− is indicated by G for WT growth, G− for growth of fewer and smaller plaques, and NG for no plaque growth. The numbers for intrachromosomal recombination indicate the average number of lac+ papillae per colony.
Basal LexA level. The relative levels of LexAEK45 are given. ++++, level with no RecA; +++, somewhat more than in the recA+ host; ++, level in a host with recA+; +, less than in recA+ host.
Cleavage by Western blotting. WT, rate of cleavage similar to that seen with WT RecA; S. def, somewhat defective; Def, some cleavage was observed but considerably less than WT; −, no cleavage detected; Constit, constitutive cleavage (that is, cleavage in the absence of nalidixic acid); Hyper, hypercleavable (that is, an increased rate relative to WT in the presence of nalidixic acid).