A single P115Q mutation modulates specificity in the Corynebacterium pseudotuberculosis arginine repressor

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• The arginine repressor (ArgR) protein controls gene expression for arginine biosynthesis.
• ArgR functions by binding arginine and then DNA, inhibiting transcription.
• Understanding ArgR's regulation is crucial for studying bacterial metabolism.

Purpose of the Study:

• To investigate the structural basis of ArgR co-repressor specificity.
• To explore how mutations affect ArgR's binding and function.
• To elucidate alternative regulatory mechanisms of ArgR in Corynebacterium pseudotuberculosis.

Main Methods:

• X-ray crystallography of wild-type and mutant ArgR.
• Molecular dynamics simulations of co-repressor binding.
• Phylogenetic analysis of ArgR sequences.

Main Results:

• A Pro115Gln mutation in ArgR switches co-repressor specificity from tyrosine to arginine.
• ArgR binds co-repressors in a trimeric state, with hexamerization occurring subsequently.
• Sodium ion binding in Pro115 ArgR hexamers shifts co-repressor selectivity back to tyrosine.
• Substitutions at position 115 and linker length influence ArgR specificity and flexibility.

Conclusions:

• Single amino acid substitutions can significantly alter ArgR co-repressor specificity.
• ArgR exhibits functional flexibility through structural adaptations.
• Alternative ArgR regulatory mechanisms may exist in Corynebacterium pseudotuberculosis.