Cyclophilin PpiB is involved in motility and biofilm formation via its functional association with certain proteins

Area of Science:

• Microbiology
• Molecular Biology
• Enzymology

Background:

• Peptidyl-prolyl cis/trans isomerases (PPIases) are crucial enzymes involved in protein folding.
• PpiB is a member of the PPIase superfamily, catalyzing rate-limiting steps in protein folding.
• The precise roles of PpiB in bacterial physiology, particularly in motility and biofilm formation, are not fully understood.

Purpose of the Study:

• To investigate the function of PpiB in regulating the motility and biofilm formation of Escherichia coli.
• To identify and characterize proteins that interact with PpiB (prey proteins) and contribute to its phenotypes.
• To elucidate the molecular mechanisms by which PpiB exerts its regulatory control over bacterial processes.

Main Methods:

• Genetic analysis involving deletion mutants (ΔppiB) and multicopy suppressor screening.
• In vivo and in vitro protein-protein interaction assays to identify PpiB prey proteins.
• Enzyme activity assays and protein localization studies to assess PpiB's functional impact on target proteins.

Main Results:

• PpiB acts as a negative regulator of motility and biofilm formation in Escherichia coli.
• Several putative prey proteins were identified, and their deletion mimicked ΔppiB phenotypes.
• PpiB directly interacts with and enhances the enzymatic activity of DnaK, AccC, and Pta, and affects protein folding and localization.

Conclusions:

• PpiB plays a significant role in negatively modulating bacterial motility and biofilm formation.
• PpiB exerts its regulatory functions through direct functional association with specific protein substrates.
• These findings reveal novel regulatory mechanisms involving PpiB in bacterial physiology.