Multiple TonB-dependent transport systems in Helicobacter pylori

Area of Science:

• Microbiology
• Bacterial Physiology
• Molecular Biology

Background:

• TonB-dependent transport systems facilitate nutrient uptake across the bacterial outer membrane.
• Tol-Pal systems share components with TonB systems.
• Helicobacter pylori possesses multiple TonB and Tol-Pal system components.

Purpose of the Study:

• To investigate the TonB-dependent transport systems in Helicobacter pylori.
• To elucidate the interactions and functions of TonB paralogs and associated proteins in H. pylori.

Main Methods:

• Immunopurification and mass spectrometry to identify protein complexes.
• Genetic analysis of tonB paralogs and their essentiality for growth.
• Inductively coupled plasma mass spectrometry (ICP-MS) to quantify metal ion levels.

Main Results:

• TonB2, ExbB2, and ExbD2 were shown to co-purify, indicating functional complex formation.
• TonB1 co-purified with ExbB3 and ExbD3.
• TonB3/TolA co-purified with ExbB1/TolQ and ExbD1/TolR, suggesting its role in the Tol-Pal system.
• H. pylori tonB1 is essential for growth, tonB2 mutants show reduced nickel and iron uptake and require supplemental iron, and tonB3/tolA is non-essential in vitro.
• TonB2 system is critical for nickel and iron acquisition, impacting urease activity.

Conclusions:

• The TonB2 system plays a significant role in H. pylori nickel and iron acquisition.
• The TonB1 system is essential for H. pylori viability, likely involved in acquiring multiple vital nutrients.
• TonB3/TolA is identified as a component of the H. pylori Tol-Pal system.