Abstract
The arginine repressor (ArgR) is an arginine-dependent transcription factor that regulates the expression of genes encoding proteins involved in the arginine biosynthesis and catabolic pathways. ArgR is a functional homolog of the arginine-dependent repressor/activator AhrC from Bacillus subtilis, and belongs to the ArgR/AhrC family of transcriptional regulators. In this research, we determined the structure of the ArgR (Bh2777) from Bacillus halodurans at 2.41 Å resolution by X-ray crystallography. The ArgR from B. halodurans appeared to be a trimer in a size exclusion column and in the crystal structure. However, it formed a hexamer in the presence of L-arginine in multi-angle light scattering (MALS) studies, indicating the oligomerization state was dependent on the presence of L-arginine. The trimeric structure showed that the C-terminal domains form the core, which was made by inter-subunit interactions mainly through hydrophobic contacts, while the N-terminal domains containing a winged helix-turn-helix DNA binding motif were arranged around the periphery. The arrangement of trimeric structure in the B. halodurans ArgR was different from those of other ArgR homologs previously reported. We finally showed that the B. halodurans ArgR has an arginine-dependent DNA binding property by an electrophoretic mobility shift assay.
Highlights
The arginine metabolism pathway is essential for various organisms and strictly controlled by the arginine repressor (ArgR) in bacteria
ArgR binds to the well-conserved DNA sequence called the ARG box in the promoter regions of the genes involved in the arginine biosynthesis and catabolic pathways in the presence of high concentration of L-arginine [5]
We determined the structure of B. halodurans ArgR in apo form
Summary
The arginine metabolism pathway is essential for various organisms and strictly controlled by the arginine repressor (ArgR) in bacteria. ArgR does regulate the transcription of nearby genes of the arginine biosynthesis regulon in the presence of L-arginine [1], but is involved in activation of the arginine catabolic pathways including arginase pathway [2], arginine deiminase pathway [3], and arginine succinyltransferase pathway [4]. ArgR binds to the well-conserved DNA sequence called the ARG box in the promoter regions of the genes involved in the arginine biosynthesis and catabolic pathways in the presence of high concentration of L-arginine [5].
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