Engineering bacterial microcompartment shells: chimeric shell proteins and chimeric carboxysome shells.

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• Bacterial microcompartments (BMCs) are protein-based organelles crucial for carbon fixation and utilization.
• Their selectively permeable protein shells regulate the passage of molecules.
• Shell proteins vary across BMC types, suggesting tunable permeability.

Purpose of the Study:

• To investigate engineering strategies for altering BMC shell permeability.
• To test the feasibility of modifying shell protein pores and constructing chimeric shells.
• To utilize carboxysomes as a model system for these engineering efforts.

Main Methods:

• Determined high-resolution crystal structures of major shell proteins (CsoS1, CcmK2) and a minor shell protein (CcmK4).
• Employed protein engineering by modifying residues flanking shell protein pores.
• Constructed chimeric shells by combining shell proteins from different BMC types.

Main Results:

• Confirmed the feasibility of engineering shell protein pores to mimic those of other shell proteins.
• Demonstrated successful construction of functional chimeric BMC shells.
• Provided structural insights into key carboxysome shell proteins.

Conclusions:

• Bacterial microcompartment shell permeability can be rationally engineered.
• Modifying pores and creating chimeric shells are viable strategies for controlling BMC function.
• This work opens avenues for designing novel BMCs with tailored properties.