| Primary Identifier | IPR036251 | Type | Homologous_superfamily |
| Short Name | Arg_repress_C_sf |
| description | The arginine dihydrolase (AD) pathway is found in many prokaryotes and some primitive eukaryotes, an example of the latter being Giardia lamblia (Giardia intestinalis) []. The three-enzyme anaerobic pathway breaks down L-arginine to form 1 mol of ATP, carbon dioxide and ammonia. In simpler bacteria, the first enzyme, arginine deiminase, can account for up to 10% of total cell protein [].Most prokaryotic arginine deiminase pathways are under the control of a repressor gene, termed ArgR []. This is a negative regulator, and will only release the arginine deiminase operon for expression in the presence of arginine []. The crystal structure of apo-ArgR from Bacillus stearothermophilus has been determined to 2.5A by means of X-ray crystallography []. 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 biosyntheis 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. The C-terminal domain of the arginine repressor is responsible for arginine binding and multimerization [, ]. It can also bind ornithine, Pro and Tyr (Matilla et. al., FEMS Microbiology Reviews, fuab043, 45, 2021, 1. https://doi.org/10.1093/femsre/fuab043). |
