Fig. 6.

Schematic model of Raf1-mediated carboxysome formation in Syn7942. Raf1 facilitates the assembly of Rubisco and Rubisco assemblies. The absence of Raf1 results in slow and inefficient assembly and labile conformations of Rubisco L₈S₈ holoenzymes, leading to less well-defined Rubisco L₈S₈ structures and an imbalance of carboxysome protein stoichiometries, which may alter the binding of CcmM to Rubisco and protein packing in the Rubisco:M35 condensate. These changes could result in the formation of small and disordered Rubisco core assemblies and interfere with shell encapsulation. As a consequence, the Δraf1 cells produce a large number of assembly intermediates without shells along with a low abundance of small carboxysome-like structures and free Rubisco.