Structural characterization of FlgE2 protein from Helicobacter pylori hook

Area of Science:

• Microbiology
• Structural Biology
• Bacterial Motility

Background:

• The Helicobacter pylori flagellum is crucial for survival in the human stomach.
• The flagellar hook, a key component, is primarily composed of the FlgE protein.
• H. pylori possesses two distinct genes encoding hypothetical FlgE proteins, FlgE1 and FlgE2, with differing identities and unknown functions for FlgE2.

Purpose of the Study:

• To elucidate the structure and potential function of the hypothetical FlgE2 protein from Helicobacter pylori.
• To investigate the role of FlgE2 in the context of the H. pylori flagellar hook organization.

Main Methods:

• Cloning and purification of the FlgE2 protein.
• Crystallization of FlgE2.
• Structure determination using single-wavelength anomalous diffraction (SAD).
• Analysis of protein domains and interactions with FlgD.

Main Results:

• The crystal structure of FlgE2 was determined, revealing a three-domain organization.
• Two domains of FlgE2 are similar to FlgE from other Gram-negative bacteria, while the third domain is unique to H. pylori.
• FlgE2 was found to interact with the regulatory cap protein FlgD.
• The findings suggest a complementary function of FlgE1 and FlgE2 in the flagellar hook.

Conclusions:

• Helicobacter pylori flagellum exhibits unique molecular organization due to the presence of two distinct hook proteins, FlgE1 and FlgE2.
• FlgE2 plays a role in flagellar hook organization, potentially in conjunction with FlgE1.
• The structural and interaction data provide insights into the specialized nature of the H. pylori flagellar nanomachine.