Cloning and preliminary characterization of srf-2020 and srf-801, the recF partial suppressor mutations which map in recA of Escherichia coli K-12

We have located the single nucleotide changes suffered in recA sequence2 recF partial suppresor mutations: srf-2020 at codon 121 and srf-801 at codon 257. srf-2020 changes codon 121 from threonine (ACC) to isoleucine (ATC). srf-801 changes codon 257 from glutamine (CAG) to proline (CCG). Consequently these mutations were renamed recA2020 and recA801 respectively. Preliminary characterization of recA2020 revealed that it is transdominant to recA⁺, like recA803, another recF partial suppressor. Interactions of recA2020 with recA803 were examined using genetic studies. Heterozygotes containing recA2020 and recA803 failed to produce a synergistic suppression effect in suppressing the recF deficiency. Presence of both recA2020 and recA803 mutations in the same recA gene also failed to produce any greater amount of UV resistance to a uvrA6recF143del(recA) strain indicating no interactions between these suppressors.