Towards engineering a hybrid carboxysome.

Area of Science:

• Biochemistry
• Synthetic Biology
• Plant Science

Background:

• Carboxysomes are bacterial microcompartments that enhance Rubisco enzyme efficiency in high CO2 environments.
• Rubisco's higher catalytic rate in carboxysomes makes them attractive for improving crop yields.
• Two carboxysome types, α and β, have distinct shell structures and Rubisco efficiencies.

Purpose of the Study:

• To investigate the potential for creating a hybrid carboxysome by combining features of α and β types.
• To test the incorporation of non-native Rubisco into simplified carboxysome-like structures.
• To assess the functional interaction between encapsulated Rubisco and carbonic anhydrase in a hybrid system.

Main Methods:

• Utilized an Escherichia coli expression system for constructing carboxysome-like structures.
• Attempted encapsulation of Thermosynechococcus elongatus Form IB Rubisco into simplified Cyanobium α-carboxysome-like structures.
• Assessed the interaction between the encapsulated Rubisco and Cyanobium carbonic anhydrase.

Main Results:

• Demonstrated imperfect incorporation of T. elongatus Form IB Rubisco into simplified α-carboxysome-like structures.
• Confirmed that while cargo encapsulation is possible, the non-native Rubisco did not interact with Cyanobium carbonic anhydrase.
• Identified a key functional requirement (enzyme interaction) for successful carboxysome assembly and function.

Conclusions:

• Successful encapsulation of non-native Rubisco into simplified carboxysome structures was achieved.
• The lack of interaction between T. elongatus Rubisco and Cyanobium carbonic anhydrase highlights a barrier to functional hybrid carboxysome formation.
• These findings provide a pathway for future engineering of functional hybrid carboxysomes.