TapA acts as specific chaperone in TasA filament formation by strand complementation

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• Bacterial biofilms are crucial for microbial resilience and communication.
• Understanding biofilm matrix components like TasA and TapA is vital.
• Bacillus subtilis biofilms offer biotechnological potential for plant protection.

Purpose of the Study:

• To elucidate the three-dimensional structure of TapA.
• To uncover the mechanism of TapA-supported growth of nonamyloidic TasA filaments.
• To investigate the structural basis of TasA filament formation.

Main Methods:

• Analytical ultracentrifugation
• Nuclear Magnetic Resonance (NMR) spectroscopy, including solid-state NMR
• Structural analysis of protein-protein interactions

Main Results:

• The study presents the 3D structure of TapA.
• TapA accelerates the formation of nonamyloidic TasA filaments.
• Solid-state NMR revealed TasA filament structure involves N-terminal peptide intercalation into beta-sandwich subunits.
• This mechanism is conserved across Gram-positive bacteria, analogous to chaperone-usher pathways.

Conclusions:

• TapA acts as a chaperone, donating its N terminus for TasA folding into Ig domain-like filaments via donor-strand complementation.
• The N-terminal strand beta0 intercalation mechanism is conserved in Gram-positive bacteria.
• Conserved residues in TasA-like proteins are located at the protomer interface, suggesting a key role in filament stability.