9V2A

The Chlamydomonas reinhardtii bicarbonate transporter LciA

Summary for 9V2A

• Entry DOI: 10.2210/pdb9v2a/pdb
• EMDB information: 64722
• Descriptor: Low-CO2 inducible protein LCIA (1 entity in total)
• Functional Keywords: chlamydomonas reinhardtii, bicarbonate transporters, lcia, co2-concentrating mechanism, transport protein
• Biological source: Chlamydomonas reinhardtii
• Total number of polymer chains: 5
• Total formula weight: 160317.08

Authors

Yang, Z.,Guo, J.,Zhang, P. (deposition date: 2025-05-19, release date: 2025-11-26, Last modification date: 2026-01-28)

Primary citation

Guo, J.,Yang, Z.,Zhang, X.,Liu, F.,Ma, M.,Yu, F.,Huang, J.,Zhang, P.
Structure of Chlamydomonas reinhardtii LciA guided the engineering of FNT family proteins to gain bicarbonate transport activity.
Nat.Plants, 2026

PubMed Abstract: Engineering functional CO-concentrating mechanisms into C crops holds great potential for enhancing photosynthetic efficiency. Limited CO-inducible A (LciA), a chloroplast envelope bicarbonate channel belonging to the formate/nitrite transporter (FNT) family, is a key algal CO2-concentrating mechanism component and has been considered as a prime candidate for introduction into C plants. However, its application has been hindered by an incomplete mechanistic understanding. Here we report the cryogenic electron microscopy structure of Chlamydomonas reinhardtii LciA. Combining structural analysis and growth assays, we determined key residues governing substrate access and permeation, and identified two substitutions (K136A/A114F) that enhance LciA activity. We found that bicarbonate selectivity is governed by electrostatic coordination mediated by Lys220 and steric constraint imposed by Ala117 and Val267 within the selectivity filter. Leveraging these insights, we successfully engineered the bacterial FNT family nitrite channel NirC through site-directed mutagenesis to gain bicarbonate transport activity, and we characterized the bicarbonate transport capacity of the Chlamydomonas nitrite channels NAR1.1/NAR1.5, which were amenable to further enhancement. Taken together, our study establishes LciA as a fundamental template for engineering and identifying FNT proteins with bicarbonate transport capability, thereby greatly expanding the molecular toolkit for synthetic biology approaches aimed at boosting photosynthetic efficiency in both algae and crops.

PubMed: 41507353
DOI: 10.1038/s41477-025-02200-9

Experimental method

ELECTRON MICROSCOPY (2.37 Å)