Structural basis of pore formation by cholesterol-binding toxins

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• Pneumolysin is a pore-forming toxin produced by Streptococcus pneumoniae.
• Cholesterol-binding toxins form pores in cell membranes, leading to cell lysis.
• Understanding the mechanism of pore formation is crucial for developing therapeutic interventions.

Purpose of the Study:

• To elucidate the structural basis of pneumolysin pore formation.
• To identify distinct oligomeric states involved in the pore formation process.
• To compare the mechanism of pneumolysin with other related toxins.

Main Methods:

• Electron cryo-microscopy was used to obtain 3D electron density maps of pneumolysin oligomers.
• Atomic models of pneumolysin domains were fitted to the electron density maps.
• Pneumolysin pores were observed in model membranes.

Main Results:

• Two distinct oligomeric states of pneumolysin were resolved.
• The fitting of atomic models revealed two key steps in the pore formation mechanism.
• The structure of the toxin pore in model membranes was visualized.

Conclusions:

• The study provides a detailed structural mechanism for pneumolysin pore formation.
• The findings contribute to understanding the broader family of cholesterol-binding toxins.
• Structural insights may guide the development of novel inhibitors.