Structural basis of Clostridium perfringens toxin complex formation

Area of Science:

• Structural biology
• Microbiology
• Biochemistry

Background:

• Clostridium perfringens is a pathogen causing disease in humans and livestock.
• Its virulence relies on potent toxins, including modular carbohydrate-active enzymes like mu-toxin and sialidases.
• Ancillary modules within these toxins are crucial for their overall function.

Purpose of the Study:

• To elucidate the structural basis of the interaction between X82 and dockerin modules in C. perfringens toxins.
• To understand the mechanism behind the ultra-tight binding observed between these modules.
• To investigate the implications of this interaction for the formation of multitoxin complexes.

Main Methods:

• Structural analysis of the X82 and dockerin module interaction.
• Characterization of hydrogen bonding and van der Waals contacts.
• Comparison of module orientation with previously studied cellulolytic complexes.

Main Results:

• An ultra-tight interaction (K(a) = 1.44 x 10(11) M(-1)) was structurally defined between X82 and dockerin modules.
• Extensive hydrogen bonding and van der Waals contacts stabilize this high-affinity complex.
• The mu-toxin dockerin module exhibits a distinct orientation compared to other dockerin-containing complexes.

Conclusions:

• The X82-dockerin interaction is a key feature of C. perfringens carbohydrate-active enzymes.
• This interaction facilitates the assembly of large, noncovalent multitoxin complexes.
• These complexes potentiate individual toxin activities through combined specificities, enhancing virulence.