Toxic component of a type II toxin-antitoxin (TA) system. A sequence-specific, ribosome-dependent mRNA endoribonuclease that inhibits translation during amino acid starvation (the stringent response). Acts by cleaving mRNA with high codon specificity in the ribosomal A site between positions 2 and 3. Acts with RelB as a corepressor of relBE transcription (By similarity). Binds DNA as a RelE(2)-RelB(2) heterotetramer. RelE occupies the A site of the 70S ribosome. RelB inhibits its endonuclease activity (By similarity). Belongs to the RelE toxin family.