YidC-driven membrane insertion of single fluorescent Pf3 coat proteins

Area of Science:

• Molecular Biology
• Biophysics
• Membrane Protein Insertion

Background:

• Bacteriophage coat proteins are essential for viral assembly and infection.
• Understanding membrane protein insertion mechanisms is crucial for various biological processes.
• The YidC protein is a known insertase involved in membrane protein biogenesis.

Purpose of the Study:

• To directly observe and characterize the membrane insertion process of single bacteriophage Pf3 coat proteins.
• To investigate the role of the YidC membrane insertase in Pf3 coat protein translocation.
• To determine the influence of protein hydrophobicity on YidC-independent membrane insertion.

Main Methods:

• Purified, fluorescently labeled bacteriophage Pf3 coat protein was used.
• Confocal fluorescence microscopy was employed to monitor protein insertion into liposomes and proteoliposomes.
• Proteoliposomes reconstituted with Escherichia coli YidC were utilized to study YidC-dependent insertion.
• Fluorescence quenching was used to differentiate surface-bound proteins from inserted proteins.

Main Results:

• The translocation of fluorescently labeled Pf3 coat protein into proteoliposomes containing YidC was detected within seconds.
• YidC was required for the membrane insertion of wild-type Pf3 coat protein.
• Mutant Pf3 coat proteins with increased membrane-spanning region hydrophobicity were capable of autonomous insertion into liposomes without YidC.

Conclusions:

• The study provides direct visualization of single bacteriophage Pf3 coat protein insertion into membranes.
• The YidC insertase plays a critical role in facilitating the membrane translocation of Pf3 coat protein.
• Increased hydrophobicity of the membrane-spanning region can enable YidC-independent protein insertion.