Purity > 90% as determined by SDS-PAGE. MW: 16.1kDa. Full Length: 1-79aa. N-terminal 10xHis-tagged and C-terminal Myc-tagged. Escherichia coli (strain K12). Antitoxin component of a type II toxin-antitoxin (TA) system. Counteracts the effect of cognate toxin RelE via direct protein-protein interaction, preventing RelE from entering the ribosome A site and thus inhibiting its endoribonuclease activity. An autorepressor of relBE operon transcription. 2 RelB dimers bind to 2 operator sequences; DNA-binding and repression is stronger when complexed with toxin/corepressor RelE by conditional cooperativity. Increased transcription rate of relBE and activation of relE is consistent with a lower level of RelB in starved cells due to degradation of RelB by protease Lon.