Arginine repressor ArgR
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| Arginine repressor, C-terminal domain | |||||||||
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 c-terminal domain of escherichia coli arginine repressor/ l-arginine complex; pb derivative | |||||||||
| Identifiers | |||||||||
| Symbol | Arg_repressor_C | ||||||||
| Pfam | PF02863 | ||||||||
| InterPro | IPR020899 | ||||||||
| SCOP2 | 1aoy / SCOPe / SUPFAM | ||||||||
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| Arginine repressor, DNA binding domain | |||||||||
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| Identifiers | |||||||||
| Symbol | Arg_repressor | ||||||||
| Pfam | PF01316 | ||||||||
| SCOP2 | 1aoy / SCOPe / SUPFAM | ||||||||
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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.