Structure of the conjugation surface exclusion protein TraT

Area of Science:

• Microbiology
• Structural Biology
• Molecular Biology

Background:

• Conjugal plasmid transfer facilitates the spread of antimicrobial resistance genes.
• Surface exclusion systems, like TraT in IncF plasmids, prevent redundant bacterial conjugation.
• Understanding these systems is crucial for combating antibiotic resistance.

Purpose of the Study:

• To determine the cryo-electron microscopy (cryo-EM) structure of the TraT exclusion protein complex from the F plasmid.
• To investigate the mechanism of TraT-mediated surface exclusion in *Escherichia coli*.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine the structure of the TraT complex.
• Microscopy-based conjugation assays with directed mutagenesis to study TraT function.

Main Results:

• The cryo-EM structure reveals TraT as a hollow homodecamer spanning the outer membrane via transmembrane α-helices.
• Mutagenesis studies indicated TraT functions via physical interference rather than specific protein interactions.
• No evidence was found for specific interactions between TraT and partner proteins.

Conclusions:

• TraT acts as a physical barrier to inhibit conjugal plasmid transfer, contributing to the control of gene spread.
• Structural insights into TraT provide a basis for understanding bacterial conjugation inhibition.
• This study elucidates a key mechanism in the regulation of microbial gene transfer.