events for the gases are also found to frequently track along the interface between the hexameric and pentameric proteins that compose the synthetic carboxysome shell model. By contrast, small anionic metabolites such as HCO3 -and 3-PGA always transit through the central pores in the hexamers and pentamers. Considering the number of CcmK hexamers and CcmL pentamers assembled together to build the icosahdedral shell (Fig. ), we would expect a 5:2 ratio of hexamer versus dimer transit events if there was no preference between the pores. However, the heavily skewed ratio observed in Fig. highlights that the negatively charged compounds transit preferentially through the abundant hexameric pores that would dot the carboxysome surface. The transit through the hexameric pore for negatively charged compounds is facilitated by the positively charged KIGT motif, instead of the conserved KIGS motif found in the central pore formed by CcmK hexamers (Fig. ).