Immunity protein protects colicin E2 from OmpT protease.

Area of Science:

• Microbiology
• Molecular Biology
• Protein Biochemistry

Background:

• Colicin E2 (ColE2) is a bacteriocidal protein produced by Escherichia coli.
• ColE2 requires the BtuB protein and Tol import machinery for entry into target cells.
• The cognate immunity protein Im2 typically protects producing cells from ColE2.

Purpose of the Study:

• To investigate the interaction between ColE2-Im2 complex and outer membrane protease OmpT.
• To determine the role of Im2 in protecting ColE2 from proteolytic degradation.
• To elucidate the mechanism of ColE2-Im2 interaction with host cell surface components.

Main Methods:

• In vivo approaches using Escherichia coli strains.
• Proteolytic cleavage assays involving OmpT protease.
• Analysis of colicin E2 and Im2 complex stability.

Main Results:

• ColE2-Im2 complex bound to sensitive cells is cleaved by OmpT.
• BtuB protein is essential for OmpT-mediated cleavage of ColE2-Im2.
• Cleavage by OmpT is enhanced when ColE2 dissociates from Im2.
• OmpT specifically cleaves the C-terminal DNase domain of ColE2.
• Strains overproducing OmpT show reduced susceptibility to ColE2 infection.

Conclusions:

• The immunity protein Im2 provides an additional protective function by shielding ColE2 from OmpT-mediated degradation.
• Im2 acts as a shield against extracellular proteolytic attack by OmpT.
• This study reveals a novel mechanism of colicin E2 regulation and survival.