Recombinant Staphylococcus aureus Argininosuccinate synthase (argG)
Description
Definition and Enzymatic Role
ArgG (EC 6.3.4.5) catalyzes the ATP-dependent condensation of citrulline and aspartate to form argininosuccinate, a key step in arginine biosynthesis. In S. aureus, ArgG operates in a non-canonical pathway that synthesizes arginine from proline instead of glutamate under carbon catabolite repression (CCR)-deficient conditions (e.g., ccpA mutants) .
Pathway Context and Genetic Regulation
ArgG functions within a urea cycle-like pathway in S. aureus:
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Proline → Glutamate-γ-semialdehyde (via PutA)
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Ornithine → Citrulline (via RocD/ArcB1)
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Citrulline + Aspartate → Argininosuccinate (via ArgG)
Key regulatory mechanisms include:
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CcpA-mediated repression: Wild-type S. aureus suppresses this pathway in glucose-rich environments. ccpA inactivation derepresses argGH expression .
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sRNA modulation: Teg58 binds argGH mRNA to inhibit translation, linking arginine biosynthesis to biofilm regulation .
Heterologous Expression and Functional Validation
Heterologous expression of S. aureus argG in Lactobacillus plantarum demonstrated its role in acid tolerance:
Table 1: Acid Stress Response in L. plantarum Expressing argG8
| Strain | ASS Activity (U/mg protein) | Intracellular Arginine (nmol/mg protein) |
|---|---|---|
| Control (pH 6.3) | 0.12 ± 0.02 | 15.3 ± 1.2 |
| Control (pH 3.7) | 0.05 ± 0.01 | 8.1 ± 0.9 |
| argG (pH 6.3) | 0.18 ± 0.03 | 24.6 ± 2.3 |
| argG (pH 3.7) | 0.39 ± 0.06 | 52.7 ± 4.8 |
Key findings:
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260% increase in ASS activity under acid stress (pH 3.7) in the argG-expressing strain.
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5.5-fold higher arginine accumulation compared to controls at pH 3.7 .
Virulence and Physiological Impact
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Mouse kidney abscess model: argH (downstream of ArgG) mutants showed attenuated virulence, confirming the pathway’s in vivo relevance .
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Metabolic flexibility: Both glutamate and proline pathways contribute to arginine synthesis in vivo, enabling redundancy during infection .
Industrial and Biotechnological Applications
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Acid-resistant probiotics: argG expression in L. plantarum enhances survival under gastrointestinal stress, with potential for engineered probiotics .
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Diagnostic tools: Antibodies targeting ArgG (e.g., recombinant antibodies 6DW2/6DWC) enable sensitive S. aureus detection (LOD: 10⁴–10⁵ CFU/mL) .
Unexplored Research Frontiers
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Structural characterization: No crystal structures of S. aureus ArgG exist, limiting mechanistic insights.
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Cross-pathway interactions: How arginine biosynthesis interfaces with nitric oxide or polyamine metabolism remains unclear.
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Therapeutic targeting: Small-molecule inhibitors of ArgG could disrupt S. aureus survival in nutrient-poor host environments.
Product Specs
Target Background
KEGG: saj:SaurJH9_0961
