Structural basis for independent pore function of Vpb4 from Bacillus thuringiensis

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• Bacterial_Exotoxin_B proteins form pores in the AB Toxin mechanism.
• The Vpb4 subclass from Bacillus thuringiensis presents a single-component system, differing from typical two-component toxins.

Purpose of the Study:

• To elucidate the pore structure of the Vpb4Aa2 protein from Bacillus thuringiensis.
• To understand the mechanistic differences between single-component and translocating pores.

Main Methods:

• Single-particle cryo-electron microscopy (cryo-EM) was used to determine the Vpb4Aa2 structure at 2.2 Å resolution.
• Electrophysiology studies were conducted to assess ion flux.

Main Results:

• The Vpb4Aa2 structure lacks a molecular bottleneck and possesses a neutrally charged β-barrel, distinguishing it from other Bacterial_Exotoxin_B members.
• Preliminary electrophysiology indicated higher ion flux for Vpb4Aa2 compared to the archetypal PA protein.

Conclusions:

• The findings reveal unique structural and functional characteristics of the Vpb4 subclass, expanding the understanding of the Bacterial_Exotoxin_B family.
• Identification of Vpb4-like proteins suggests a broader class of single-component pore-forming proteins.
• This research has implications for the agricultural industry in identifying novel pest control agents.