This family consists of the C-terminal helix-turn-helix domain found in several bacterial GTP-sensing transcriptional pleiotropic repressor CodY proteins. CodY has been found to repress the dipeptide transport operon (dpp) of Bacillus subtilis in nutrient-rich conditions [1]. The CodY protein also has a repressor effect on many genes in Lactococcus lactis during growth in milk [2].

1: A gene required for nutritional repression of the Bacillus subtilis dipeptide permease operon. Slack FJ, Serror P, Joyce E, Sonenshein AL; Mol Microbiol 1995;15:689-702. PMID:7783641

2: Pleiotropic transcriptional repressor CodY senses the intracellular pool of branched-chain amino acids in Lactococcus lactis. Guedon E, Serror P, Ehrlich SD, Renault P, Delorme C; Mol Microbiol 2001;40:1227-1239. PMID:11401725