The Direct Interaction between Two Morphogenetic Proteins Is Essential for Spore Coat Formation in Bacillus subtilis

Area of Science:

• Microbiology
• Bacterial spore formation
• Protein-protein interactions

Background:

• Bacillus subtilis spores possess protective layers composed of over seventy proteins.
• Morphogenetic factors regulate the assembly of spore coat proteins.
• CotE is a key morphogenetic factor organizing outer spore layers, and CotH is CotE-dependent, controlling assembly of nine other proteins.

Purpose of the Study:

• To investigate the regulatory relationship between CotH and CotE.
• To elucidate the mechanism underlying the interaction between CotH and CotE.

Main Methods:

• Investigated protein-protein interactions using mutant CotE variants.
• Analyzed the role of CotE's C-terminal end in CotH binding.
• Assessed the effect of specific amino acid substitutions on CotH-CotE interaction.

Main Results:

• CotH regulates CotE assembly, revealing a mutual dependency.
• CotH and CotE directly interact.
• The C-terminal end of CotE is essential for CotH binding; deletion mutants show impaired interaction.
• Adding a negative charge to deleted CotE variants rescues CotH interaction.

Conclusions:

• CotH and CotE exhibit a mutual regulatory relationship essential for Bacillus subtilis spore coat assembly.
• Direct interaction between CotH and CotE, mediated by CotE's C-terminus, is critical.
• The C-terminal region of CotE plays a vital role in orchestrating spore coat formation through its interaction with CotH.