Clostridium perfringens Beta2 toxin forms highly cation-selective channels in lipid bilayers

Area of Science:

• Microbiology
• Biochemistry
• Toxicology

Background:

• Clostridium perfringens produces various toxins, including five well-studied toxins (alpha, Beta (CPB), epsilon, iota, and CPE) from toxinotypes A-G.
• A distinct toxin, consensus Beta2 toxin (cCPB2), is associated with necrotizing enterocolitis in piglets and has unknown cellular actions.

Purpose of the Study:

• To elucidate the primary cellular action of consensus Beta2 toxin (cCPB2).
• To characterize the biophysical properties of cCPB2 in lipid bilayers.

Main Methods:

• Heterologous expression and purification of cCPB2 as a GST-fusion protein in Escherichia coli.
• Electrophysiological recordings of cCPB2 activity in lipid bilayers to determine channel conductance and ion selectivity.
• Bioinformatic analysis to construct a phylogenetic cladogram of cCPB2 homologs.

Main Results:

• cCPB2 functions as a pore-forming protein in lipid bilayers, despite lacking typical pore-forming structural motifs.
• The formed channels exhibit high cation selectivity and a conductance of approximately 700 pS in 1 M KCl.
• Channel analysis suggests a pore width of about 1.4 nm, attributed to net negative charges within the channel.

Conclusions:

• The primary mechanism of cCPB2 toxicity involves the formation of cation-selective channels.
• This pore-forming activity is the likely cause of necrotic enteritis observed in humans and animals.
• Phylogenetic analysis provides insights into the evolutionary relationships of cCPB2.