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- PDB-9v2a: The Chlamydomonas reinhardtii bicarbonate transporter LciA -

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Basic information

Entry
Database: PDB / ID: 9v2a
TitleThe Chlamydomonas reinhardtii bicarbonate transporter LciA
ComponentsLow-CO2 inducible protein LCIA
KeywordsTRANSPORT PROTEIN / Chlamydomonas reinhardtii / bicarbonate transporters / LciA / CO2-concentrating mechanism
Function / homologyformate transport / formate transmembrane transporter activity / Formate/nitrite transporter / Formate/nitrite transporter / Aquaporin-like / plasma membrane / Low-CO2 inducible protein LCIA
Function and homology information
Biological speciesChlamydomonas reinhardtii (plant)
MethodELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 2.37 Å
AuthorsYang, Z. / Guo, J. / Zhang, P.
Funding support China, 1items
OrganizationGrant numberCountry
National Natural Science Foundation of China (NSFC)32401000 China
CitationJournal: Nat Plants / Year: 2026
Title: Structure of Chlamydomonas reinhardtii LciA guided the engineering of FNT family proteins to gain bicarbonate transport activity.
Authors: Jiaxin Guo / Zhao Yang / Xue Zhang / Feifan Liu / Miaolian Ma / Fang Yu / Jirong Huang / Peng Zhang /
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 ...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.
History
DepositionMay 19, 2025Deposition site: PDBJ / Processing site: PDBC
Revision 1.0Nov 26, 2025Provider: repository / Type: Initial release
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Structure visualization

Structure viewerMolecule:
MolmilJmol/JSmol

Downloads & links

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Assembly

Deposited unit
A: Low-CO2 inducible protein LCIA
B: Low-CO2 inducible protein LCIA
C: Low-CO2 inducible protein LCIA
D: Low-CO2 inducible protein LCIA
E: Low-CO2 inducible protein LCIA


Theoretical massNumber of molelcules
Total (without water)160,3175
Polymers160,3175
Non-polymers00
Water00
1


  • Idetical with deposited unit
  • defined by author
  • Evidence: electron microscopy, not applicable
TypeNameSymmetry operationNumber
identity operation1_5551

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Components

#1: Protein
Low-CO2 inducible protein LCIA / NAR1.2


Mass: 32063.416 Da / Num. of mol.: 5
Source method: isolated from a genetically manipulated source
Source: (gene. exp.) Chlamydomonas reinhardtii (plant) / Gene: LciA, CHLRE_06g309000v5 / Production host: Homo sapiens (human) / References: UniProt: Q75NZ3
Has protein modificationN

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Experimental details

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Experiment

ExperimentMethod: ELECTRON MICROSCOPY
EM experimentAggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction

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Sample preparation

ComponentName: Low-CO2 inducible protein LciA / Type: COMPLEX / Entity ID: all / Source: RECOMBINANT
Source (natural)Organism: Chlamydomonas reinhardtii (plant)
Source (recombinant)Organism: Homo sapiens (human)
Buffer solutionpH: 7.5
SpecimenConc.: 27 mg/ml / Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES
VitrificationCryogen name: ETHANE

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Electron microscopy imaging

Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
MicroscopyModel: TFS KRIOS
Electron gunElectron source: FIELD EMISSION GUN / Accelerating voltage: 300 kV / Illumination mode: FLOOD BEAM
Electron lensMode: BRIGHT FIELD / Nominal defocus max: 2200 nm / Nominal defocus min: 1200 nm
Image recordingElectron dose: 50 e/Å2 / Film or detector model: TFS FALCON 4i (4k x 4k)

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Processing

EM softwareName: PHENIX / Version: 1.14_3260 / Category: model refinement
CTF correctionType: PHASE FLIPPING AND AMPLITUDE CORRECTION
3D reconstructionResolution: 2.37 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 169175 / Symmetry type: POINT

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