Initial characterization of the hemolysin stachylysin from Stachybotrys chartarum

Area of Science:

• Mycology
• Toxicology
• Biochemistry

Background:

• Stachybotrys chartarum is a toxigenic fungus linked to human health problems.
• The fungus produces stachylysin, a hemolysin implicated in these health concerns.

Purpose of the Study:

• To characterize the molecular properties and hemolytic activity of stachylysin.
• To understand the active form of stachylysin and its mechanism of action.

Main Methods:

• Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was used to determine molecular mass.
• Hemolytic assays were performed on sheep erythrocytes.
• Stachylysin was subjected to dialysis and heat treatment for inactivation studies.

Main Results:

• Stachylysin's apparent monomeric form has a molecular mass of 11,920 Da.
• Stachylysin forms polydispersed aggregates, complicating the identification of the active form.
• Inactivation was achieved through exhaustive dialysis or heat treatment (60°C for 30 min).
• Stachylysin comprises approximately 40% nonpolar amino acids and contains two cysteine residues.
• Lysis of sheep erythrocytes began after 6 hours and was complete by 48 hours.
• Stachylysin was observed to form pores in erythrocyte membranes.

Conclusions:

• Stachylysin is a complex hemolysin produced by Stachybotrys chartarum.
• Its aggregation and pore-forming activity are key features of its hemolytic mechanism.
• Understanding stachylysin's properties is crucial for assessing health risks associated with this fungus.