| Symbol: | Arg_repressor_C |
| Arginine repressor, C-terminal domain | |
| Pfam: | PF02863 |
| Interpro: | IPR020899 |
| Scop: | 1aoy |
| Symbol: | Arg_repressor |
| Arginine repressor, DNA binding domain | |
| Pfam: | PF01316 |
| Scop: | 1aoy |
In molecular biology, the arginine repressor (ArgR) is a repressor of prokaryotic arginine deiminase pathways.
The arginine dihydrolase (AD) pathway is found in many prokaryotes and some eukaryotes, an example of the latter being Giardia lamblia (Giardia intestinalis).[1] The three-enzyme anaerobic pathway breaks down L-arginine to form 1 mol of ATP, carbon dioxide and ammonia. In some bacteria, the first enzyme, arginine deiminase, can account for up to 10% of total cell protein.[1]
Most prokaryotic arginine deiminase pathways are under the control of a repressor gene, termed ArgR.[2] This is a negative regulator, and will only release the arginine deiminase operon for expression in the presence of arginine.[3] The crystal structure of apo-ArgR from Bacillus stearothermophilus has been determined to 2.5A by means of X-ray crystallography.[4] The protein exists as a hexamer of identical subunits, and is shown to have six DNA-binding domains, clustered around a central oligomeric core when bound to arginine. It predominantly interacts with A.T residues in ARG boxes. This hexameric protein binds DNA at its N terminus to repress arginine biosynthesis or activate arginine catabolism. Some species have several ArgR paralogs. In a neighbour-joining tree, some of these paralogous sequences show long branches and differ significantly from the well-conserved C-terminal region.