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Applying an Inducible Expression System to Study Interference of Bacterial Virulence Factors with Intracellular Signaling
Published on: June 25, 2015
Bacillus anthracis virulence regulator AtxA: oligomeric state, function and CO(2) -signalling.
Troy G Hammerstrom1, Jung Hyeob Roh, Edward P Nikonowicz
1Department of Microbiology and Molecular Genetics, The University of Texas - Houston Health Science Center, Medical School, Houston, TX, USA.
Molecular Microbiology
|September 20, 2011
Summary
AtxA protein, a key regulator of Bacillus anthracis virulence, forms dimers essential for its function. Host signals like CO2 enhance AtxA dimer formation, boosting virulence gene expression.
Area of Science:
- Microbiology
- Molecular Biology
- Protein Biochemistry
Background:
- AtxA is a regulatory protein controlling Bacillus anthracis virulence genes.
- Its molecular function and interaction mechanisms are largely unknown.
- AtxA shares sequence similarities with proteins in the phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS).
Purpose of the Study:
- To investigate the molecular function and protein-protein interactions of AtxA.
- To determine the oligomeric state of AtxA and identify interaction sites.
- To explore the influence of host-associated signals on AtxA activity.
Main Methods:
- Co-affinity purification and bis(maleimido)hexane (BMH) cross-linking were used to study AtxA interactions.
- Non-denaturing polyacrylamide gel electrophoresis analyzed protein oligomerization.
- Site-directed mutagenesis (Cys→Ser substitutions) identified critical cysteine residues for cross-linking.
Main Results:
- AtxA forms homo-multimers, with dimers being the most abundant species.
- Cysteine 402 (C402) is crucial for BMH cross-linking, indicating its role in intermolecular bonding, but not essential for dimerization itself.
- Elevated CO2/bicarbonate levels increased the AtxA dimer/monomer ratio and enhanced AtxA activity.
Conclusions:
- AtxA likely functions as a dimer, and its oligomerization is modulated by host-associated signals.
- The identified EIIB motif in AtxA may play a role in protein oligomerization.
- Environmental cues like CO2 can regulate bacterial virulence through AtxA dimerization.
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