Structure of a type IV secretion system core complex encoded by multi-drug resistance F plasmids

Area of Science:

• Microbiology
• Structural Biology
• Molecular Biology

Background:

• Bacterial type IV secretion systems (T4SSs) are critical for the spread of multi-drug resistance.
• Understanding T4SS structure is essential for combating antibiotic resistance.

Purpose of the Study:

• To determine the high-resolution structure of the F plasmid outer-membrane core complex (OMCC_F).
• To elucidate the structural mechanisms underlying T4SS function and F plasmid dissemination.

Main Methods:

• Cryoelectron microscopy was used to solve the OMCC_F structure at <3.0 Å resolution.
• Analysis of protein-protein interactions and symmetry within the complex.

Main Results:

• The OMCC_F comprises a 13-fold symmetrical outer ring complex (ORC) and a 17-fold symmetrical central cone (CC).
• Proteins TraK, TraV, and TraB form the OMCC_F, exhibiting domain rearrangements to accommodate symmetry mismatches.
• Additional pED208 factors stabilize the complex architecture.

Conclusions:

• The study defines the structural basis of the OMCC_F, highlighting key domains for T4SS function.
• Identified structural motifs are important for F plasmid dissemination and F pilus biogenesis.
• This work provides a foundation for targeting T4SSs to combat antibiotic resistance.