RadD contains helicase motifs, suggesting it may be a helicase, although that activity has not been observed (Probable). In combination with RadA is important in repair of double-strand DNA breaks (DSB) (PubMed:25425430, PubMed:25484163). Has DNA-independent ATPase activity that is stimulated by single-stranded DNA-binding protein SSB. ATPase is stimulated by a peptide with the last 10 residues of SSB, but not when the peptide's last Phe residue is missing. Binds ssDNA; binding is slightly better in the presence of nucleotides (PubMed:27519413). May be involved in resolution of branched DNA intermediates that result from template switching in postreplication gaps. Binds to DNA structures with 3 branches that resemble replication forks (PubMed:31665437). ATP + H2O = ADP + H(+) + phosphate ATPase activity in the presence of KCl in the absence of any nucleic acid substrate. Optimum pH is >7.5. Monomer (PubMed:31035307, PubMed:27519413). Interacts with single-stranded DNA-binding protein SSB (PubMed:27519413). The C-terminal domain (residues 356-586) is required to alleviate the deleterious effects of UV or ciprofloxacin (CFX) treatment in a double radA-radD mutant; its effect on ionising irradiation (IR) survival in the single radD mutant were not reported (PubMed:25425430). Crystals have 4 domains; helicase ATP-binding (residues 7-185), helicase C-terminal (residues 187-365), a zinc finger domain (residues 376-425) and the C-terminal domain (429-574) (PubMed:31035307). 100- to 10000-fold decrease in survival after IR (PubMed:25049088, PubMed:25425430). Double radA-radD deletions have nearly 10(6)-fold lower survival upon IR, and the double mutant is more severely affected by UV radiation than either of the single mutants alone (up to 100 J/m(2)). The single mutation is more sensitive to dsDNA breaks induced by CFX, the double radA-radD mutant is inviable upon CFX treatment; the SOS response is slightly induced in the single and more induced in the double mutant. No effect on RecA-mediated conjugational DNA recombination (PubMed:25425430). In another study double radA-radD deletions are sensitive to CFX but not to UV (up to 40 J/m(2)) or azidothymidine (AZT) (PubMed:25484163). Deletion of radD leads to an increase in DNA crossing over, DNA repeat deletion and DNA repeat expansion; double uup-radD deletion increases the phenotypes. Single radD deletion has no effect on cell growth or filamentation, double uup-radD deletions are filamentous and lack defined nucleoids. Single deletion is more sensitive to CFX (PubMed:31665437).