Toxic component of a type I toxin-antitoxin (TA) system. Upon overexpression inhibits growth and reduces colony-forming units in both the presence and absence of the Rac prophage, cells become filamentous. Has deoxyribonuclease activity (probably endonucleolytic), does not digest RNA. Its toxic effects are neutralized by sRNA antitoxin RalA, which is encoded in trans on the opposite DNA strand (PubMed:24748661). Has RAL-like activity (PubMed:7476171). Inhibited by EDTA. The sRNA antitoxin RalA probably works by inhibiting translation of the RalR mRNA. The ability of RalA to block the toxicity of RalR relies on a 16-nt sequence which is complementary to a section of the RalR coding region; in the presence of RalA sRNA decreased amounts of RalR protein accumulate with no significant changes in the level of RalR RNA. The single ralR and double ralR-ralA mutant have increased sensitivity to the antibiotic fosfomycin. This protein is encoded on the Rac prophage. Extended N-terminus.