The C-terminal domain of several bacterial transcriptional repressors show structural homology to one another. These domains are characterised by an SH3-like structure consisting of a partly opened beta-barrel, where the last strand is interrupted by a 3-10 helical turn. The C-terminal domain displays a metal-binding function in DTXR and IDER and may act to stabilizing the dimeric form of the Escherichia coli KorB repressor, thereby enhancing specific operator binding by the repressor. The N-terminal region of these proteins is responsible for binding DNA.
Proteins containing this C-terminal domain include: the Escherichia coli biotin repressor BirA, which has the dual role of a transcriptional repressor of the biotin operator and a biotin-activating enzyme [1409631, 11353844]; the E. coli RP4 plasmid regulatory protein KorB, which regulates the expression of plasmid genes whose products are involved in the replication, transfer, and inheritance of RP4 ; and the diphtheria toxin repressor (DTXR), along with its homologues in the pathogenic bacteria causing tuberculosis (IDER), leprosy, syphilis, and staphylococcal infections, which play important roles in regulating virulence-associated genes [11320302, 11053439].