Evidence for Improved Encapsulated Pathway Behavior in a Bacterial Microcompartment through Shell Protein...

Area of Science:

• Cell biology
• Biochemistry
• Synthetic biology

Background:

• Bacterial microcompartments are protein shells enclosing enzymes, crucial for preventing intermediate escape and side reactions.
• Engineering synthetic microcompartments can enhance heterologous pathway function, but controlling metabolite diffusion is key.

Purpose of the Study:

• To investigate how structural changes in shell proteins affect metabolite diffusion across bacterial microcompartments.
• To identify strategies for controlling metabolite transport in engineered microcompartments.

Main Methods:

• Incorporated the ethanolamine utilization (Eut) protein EutM into 1,2-propanediol utilization (Pdu) microcompartments.
• Introduced single pore-lining residue mutations in shell proteins.
• Analyzed growth on 1,2-propanediol as the sole carbon source.
• Evaluated the impact of hydropathy index and charge of pore amino acids.

Main Results:

• EutM incorporation into Pdu microcompartments altered metabolite accumulation and improved growth on 1,2-propanediol.
• A single pore mutation mimicked the effect of EutM substitution, confirming diffusion control.
• Hydropathy and charge of pore amino acids predict growth effects, likely by regulating metabolite diffusion.

Conclusions:

• Small molecule diffusion through microcompartment shells can be modulated by altering shell protein structure.
• Strategies for engineering microcompartments include mutating pore-lining residues and creating protein chimeras.
• This work provides insights into controlling metabolite transport for enhanced metabolic engineering.