Fig. 7.

Tentative model showing the proposed physiological role of BST1–3 in the CCM of Chlamydomonas. Known transporters (LCI1, HLA3, and LCIA) are indicated on the plasma membrane and chloroplast, respectively. Solid line arrows indicate the movement of HCO₃⁻ into the thylakoid by BST1–3. Dashed lines indicate the proposed leakage-reducing pathway that involves recycling CO₂ by LCIB/C back to HCO₃⁻. The dotted black line represents the light-driven establishment of a proton gradient across the thylakoid membrane by PSII and the cytochrome b6f complex of the photosynthetic electron transport chain (PETC).