Encapsulation mechanisms and structural studies of GRM2 bacterial microcompartment particles

Area of Science:

• Biochemistry
• Structural Biology
• Synthetic Biology

Background:

• Bacterial microcompartments (BMCs) are protein-bound organelles found in prokaryotes.
• They compartmentalize metabolic pathways, including choline, glycerol, and ethanolamine degradation, and carbon fixation.
• Understanding BMC assembly is crucial for synthetic biology applications aiming to encapsulate non-native enzymes.

Purpose of the Study:

• To investigate the assembly mechanisms of BMCs and the encapsulation of their enzymatic cores.
• To characterize the structure of BMC shell particles.
• To explore the potential of BMCs in synthetic biology.

Main Methods:

• Isolation and recombinant expression of BMC structural genes from Klebsiella pneumoniae.
• Cryo-electron microscopy (cryo-EM) for structural characterization.
• Analysis of enzyme encapsulation processes.

Main Results:

• Demonstrated a hierarchical mechanism for enzymatic core encapsulation within BMCs.
• Identified CutC choline lyase as a potential adaptor protein in the encapsulation process.
• Determined a cryo-EM structure of a p=4 icosahedral shell particle at 3.3 Å resolution.
• Observed variability in minor shell forms.

Conclusions:

• BMCs encapsulate their enzymatic cores through a hierarchical process.
• The CutC enzyme may act as an adaptor protein, facilitating core encapsulation.
• The high-resolution structure provides insights into BMC assembly and potential for synthetic biology.