The omega transcriptional repressor regulates expression of involved in copy number control and stable maintenance of plasmids. The omega protein belongs to the structural superfamily of MetJ/Arc repressors featuring a ribbon-helix-helix DNA-binding motif with the beta-ribbon located in and recognising the major groove of operator DNA [1].

1: Crystal structure of omega transcriptional repressor encoded by Streptococcus pyogenes plasmid pSM19035 at 1.5 A resolution. Murayama K, Orth P, de la Hoz AB, Alonso JC, Saenger W; J Mol Biol 2001;314:789-796. PMID:11733997