A cellulosomal double-dockerin module from Clostridium thermocellum shows distinct structural and cohesin-binding...

Area of Science:

• Biochemistry
• Molecular Biology
• Biotechnology

Background:

• Cellulosomes are complex enzyme systems in anaerobic bacteria crucial for cellulose degradation.
• Cellulosome assembly involves cohesin-enzyme interactions, with scaffoldin proteins organizing enzymes via dockerin modules.
• The function of rare tandem dockerin modules remains largely unknown.

Purpose of the Study:

• To elucidate the structure and assembly mechanism of a novel tandem bimodular double-dockerin from Clostridium thermocellum.
• To investigate the binding interactions of this double-dockerin with cohesin modules.

Main Methods:

• X-ray crystallography and Nuclear Magnetic Resonance (NMR) spectroscopy for structural determination.
• Isothermal titration calorimetry and NMR titration for analyzing binding affinities and interactions.

Main Results:

• The double-dockerin possesses two type I dockerin folds with inter-module interactions.
• It preferentially binds the scaffoldin ScaD via the first dockerin, while the second dockerin shows no binding to resident cohesins.
• Higher affinity was observed for a cohesin from Clostridium cellulolyticum's CipC scaffoldin.

Conclusions:

• The study provides structural and interaction insights into double-dockerin modules, suggesting a role in cellulosome complexity.
• Findings pave the way for functional studies on multiple-dockerin modules and associated proteases.
• Highlights the intricate diversity of cellulosome assembly mechanisms.